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.... BY HARRY HARRISON Because there were few adults in the crowd, and Colonel "Biff" Hawton stood over six feet tall, he could see every detail of the demonstration. The children—and most of the parents—gaped in wide-eyed wonder. 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 just the way a ship rides the waves in the ocean. Now watch...." Every eye was on him as he put the gaudy model rocketship on top of the table and stepped back. It was made of stamped metal and seemed as incapable of flying as a can of ham—which it very much resembled. Neither wings, propellors, nor jets broke through the painted surface. It rested on three rubber wheels and coming out through the bottom was a double strand of thin insulated wire. This white wire ran across the top of the An indicator light, a switch and a knob appeared to be the only controls. with the powers of the whole world here...." A concerted the air. The demonstrator stepped 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 the table. "Only $17.95," the young man said, putting a large price sign on the 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 noisy passage, and after a moment he sank into a gloomy silence. He put the control box down, yawned and sat on the edge of the table. Colonel 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 at each end of the ship." With a pencil he pointed out the odd shaped plastic forms about an inch in diameter 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 "What you mean to say," Biff cheap rheostat to those meaningless worth of tin, I want to know what I'm getting." The demonstrator flushed. "I'm 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 "Sold, my boy!" the colonel said, 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?" The demonstrator looked around carefully, then pointed. "Strings!" he said. "Or rather a black thread. It runs from the top of the model, through a tiny loop in the ceiling, 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 black cloth will do," the young man good site, just see that the room in 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 cheered and jeered as he hammed up the introduction. "Let me copy the diagram, Biff, I cheaper than lox, this is the thing of the future!" Only Teddy Kaner caught wise as 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 by one. The colonel was a good showman 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 "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 through it with the whole works." ILLUSTRATED BY BREY 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. 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," the young man said. "One week getting fallen arches, demonstrating those toy ships for every brat within must have cost at least a hundred dollars apiece to make." "But you did sell the ten of them the older man asked. "I think so, I caught a few Air Force officers and a colonel in missiles one day. Then there was one official I remembered from the Bureau of Standards. Luckily he didn't recognize reduction in weight around them when they are operating...." "But a small reduction. And we don't know what is causing it. No one can be interested in a thing like that—a fractional weight decrease in a clumsy model, certainly not enough to lift the weight of the generator. No one wrapped up in massive fuel consumption, tons of lift and such is 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 impatiently. "I know they will. The tensile strength of that thread is correctly adjusted 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 thinking about it and worrying about 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 comes to manufacture," the young man said cynically. "We'll all be rich, son," the older "Believe me, you're not going to recognize this old world ten years from now."

<question>:
What was ironic about the colonel saying that all good illusions are simple?

<options>:
A It wasn't ironic
B He did not see the thread until it was pointed out to him
C The illusion would be spotted by one of his friends
D The illusion was more complicated than he realized

<answer>:

D