Read the following passage and questions, then choose the right answer from options, the answer should be one of A, B, C, D.

<passage>:
The gadget was strictly, beyond any question, a toy. Not a real, workable device. Except for the way it could work under a man's mental skin.... Because there were few adults in see every detail of the demonstration. The children—and most of the Biff Hawton was too sophisticated to be awed. He stayed on because he wanted to find out what the trick was that made the gadget work. "It's all explained right here in your instruction book," the demonstrator said, holding up a garishly printed booklet opened to a four-color diagram. "You all know how magnets pick up things and I bet you even know that the earth itself is one great big magnet—that's why compasses always point north. Well ... the Atomic Wonder Space Wave Tapper hangs onto those space waves. Invisibly all about us, and it very much resembled. Neither black table and terminated in a control box in the demonstrator's hand. An indicator light, a switch and a knob appeared to be the only controls. "I turn on the Power Switch, sending a surge of current to the Wave Receptors," he said. The switch clicked and the light blinked on and off with a steady pulse. Then the man began to slowly turn the knob. "A careful touch on the Wave Generator is necessary as we are dealing with the powers of the whole world here...." A concerted back and the toy rose higher and higher, bobbing gently on the invisible waves of magnetic force that supported it. Ever so slowly the power was reduced and it settled back to table. "For the complete set of the Atomic Wonder, the Space Tapper control box, battery and instruction book ..." At the appearance of the price card the crowd broke up noisily and the children rushed away towards the operating model trains. The demonstrator's words were lost in their sank into a gloomy silence. He put Hawton was the only one left after the crowd had moved on. "Could you tell me how this thing works?" the colonel asked, coming forward. The demonstrator brightened up and picked up one of the that had been wound—apparently at random—with a few turns of copper wire. Except for these coils the interior of the model was empty. The coils were wired together and other wires ran out through the hole in the bottom of the control box. Biff Hawton turned a very quizzical eye on the gadget and upon the demonstrator who completely ignored this sign of disbelief. "Inside the control box is the battery," the young man said, snapping it open and pointing to an ordinary flashlight battery. "The current goes through the Power Switch and Power Light to the Wave Generator ..." "What you mean to say," Biff broke in, "is that the juice from this fifteen cent battery goes through this cheap rheostat to those meaningless coils in the model and absolutely nothing happens. Now tell me what sorry, sir," he stammered. "I wasn't trying to hide anything. Like any magic trick this one can't be really demonstrated until it has been purchased." He leaned forward and whispered confidentially. "I'll tell you what I'll do though. This thing is way overpriced and hasn't been moving at all. The manager said I could let them slamming three bills down on the table. "I'll give that much for it no matter how it works. The boys in the shop will get a kick out of it," he tapped the winged rocket on his —what holds it up?" runs from the top of the model, through a tiny loop in the ceiling, and back down to my hand—tied to this ring on my finger. When I back up—the model rises. It's as simple as that." "All good illusions are simple," the colonel grunted, tracing the black thread with his eye. "As long as there is plenty of flimflam to distract the viewer." "If you don't have a black table, a back is dark." "Wrap it up, my boy, I wasn't born yesterday. I'm an old hand at this kind of thing." Biff Hawton sprang it at the next Thursday-night poker party. The gang were all missile men and they "Let me copy the diagram, Biff, I could use some of those magnetic waves in the new bird!" "Those flashlight batteries are cheaper than lox, this is the thing of the future!" the flight began. He was an amateur magician and spotted the gimmick at once. He kept silent with professional courtesy, and smiled ironically as the rest of the bunch grew silent one and he had set the scene well. He almost had them believing in the Space Wave Tapper before he was through. When the model had landed and he had switched it off he couldn't stop them from crowding around the table. "A thread!" one of the engineers shouted, almost with relief, and they all laughed along with him. "Too bad," the head project physicist said, "I was hoping that a little Space Wave Tapping could help us out. Let me try a flight with it." "He spotted it while you were all watching the flashing lights, only he didn't say anything." Kaner slipped the ring with the black thread over his finger and started to step back. "You have to turn the switch on first," Biff said. "I know," Kaner smiled. "But that's part of illusion—the spiel and the misdirection. I'm going to try this cold first, so I can get it moving up and down smoothly, then go He moved his hand back smoothly, in a professional manner that drew no attention to it. The model lifted from the table—then crashed back down. "The thread broke," Kaner said. "You jerked it, instead of pulling smoothly," Biff said and knotted the broken thread. "Here let me show you how to do it." The thread broke again when Biff tried it, which got a good laugh that made his collar a little warm. Someone mentioned the poker game. This was the only time that poker was mentioned or even remembered that night. Because very soon after this they found that the thread would lift the model only when the switch was on and two and a half volts flowing through the joke coils. With the current turned off the model was too heavy to lift. The thread broke every time. "I still think it's a screwy idea," to people who would be interested?" you spotted from the university." "Then the problem is out of our hands and into theirs. All we have to do now is sit back and wait for results." " What results?! These people weren't interested when we were hammering on their doors with the proof. We've patented the coils and can prove to anyone that there is a reduction in weight around them when they are operating...." "But a small reduction. And we don't know what is causing it. No that—a fractional weight decrease in a clumsy model, certainly not enough to lift the weight of the generator. going to have time to worry about a crackpot who thinks he has found a minor slip in Newton's laws." "You think they will now?" the young man asked, cracking his knuckles "I know they will. The tensile strength of that thread is correctly adjusted to the weight of the model. The thread will break if you try to lift the model with it. Yet you can lift the model—after a small increment of its weight has been removed by the coils. This is going to bug them to solve the problem or concern themselves with it. But it will nag at them because they know this effect can't possibly exist. They'll see at once that the magnetic-wave theory is nonsense. Or perhaps true? We don't know. But they will all be it. Someone is going to experiment in his basement—just as a hobby of course—to find the cause of the error. And he or someone else is going to find out what makes those coils work, or maybe a way to improve them!" "And we have the patents...." "Correct. They will be doing the research that will take them out of flight." "And in doing so they will be making us rich—whenever the time comes to manufacture," the young

<question>:
What distracts Biff and his friends from continuing their poker game?

<options>:
A They can't figure out how to do the trick because the thread keeps breaking.
B They get called to duty from the military.
C The demonstrator arrives to sell more gadgets.
D They discover that the trick only works when the power button is on.

<answer>:

D