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

<passage>:
SILENCE IS—DEADLY By Bertrand L. Shurtleff Radio is an absolute necessity in modern organization—and particularly in modern naval organization. If you could silence all radio—silence of that sort would be deadly! [Transcriber's Note: This etext was produced from Astounding Science-Fiction April 1942. The hurried rat-a-tat of knuckles hammered on the cabin door. Androka had arrived on board the radio station on a high promontory on the north shore of the islet. Another had found the remains of tents and log cabins, recently demolished, in a small, timbered hollow—a well-hidden spot invisible from the air, unless one were flying very low behind. Curtis was studying the wreckage of the wireless station, wondering if this might have been the source of Androka's zone of silence, when Ensign Jack Dillon came up to him. Androka, with a quizzical grin. "Old Czech-and-Double-Czech is working "Call up to the bridge to stop her," he told Nelson. "We can't afford to move in these waters with such a possibility of error!" Nelson complied, and the throbbing drive of the engines lessened at once. Nelson said: "I've been wondering, sir, if it wouldn't be advisable to try getting a radio cross-bearing. With all these rocks and islets—" "Radio?" repeated the little Czech, thrusting his face between the other two, in his independent fashion that ignored ship's discipline. old eyes twinkling behind their thick lenses. "Go ahead and try it. See how much you can get! It will be no more than Hitler can get when Zukor Androka decrees silence over the German airways! Try it! Try it, I say!" Bob Curtis stared at him, as if questioning his sanity. Then he hastened to the radio room, with Nelson at his heels, and the Czech trotting along behind. The door burst open as they neared it. A frightened operator came out, still wearing his earphones, and stood staring upward incredulously at the aërial. "Get us a radio cross-bearing for location at once," Curtis said thrust himself into the radio room. "Try again!" he told the operator. "See what you can get!" The radio man leaped to his seat and tried frantically. Again and again, he sent off a request for a cross-bearing from shore stations that had recently been established to insure safety to naval vessels, but there was no answer on any of the bands—not even the blare of a high-powered commercial program in the higher reach, nor the chatter of ships or amateurs on the shorter. gentlemen! The set is uninjured. The waves are what have been upset. I have shattered them around your ship, just as I can eventually shatter them all over Central Europe! For the next two hours, no radio messages can enter or leave my zone of radio silence—of refracted radio waves, set up by my little station on one of the neighboring islets!" There was a long pause, while commander and navigator stared at him. "Your secrecy might well cost the United States navy one of its best light cruisers—and us our lives!" he said angrily. "We need that check by radio at once! If you're not talking nonsense, call off your dogs till we learn just where we are!" Androka held out his palms helplessly. "I can do nothing. I have given orders to my assistant that he must keep two hours of radio silence! I can get no message to him, for our radio is dead!" As if to mock him, the ship's radio began to answer: winking at the two officers over Androka's discomfiture, and asked for numbers. Ignoring the gibbering Androka, who was wailing his closed. The sky was again a blanket of darkness pouring sheets of rain at them. cabin. Curtis lingered in the wireless room with the radio operator. "It's a funny thing," the latter said, still dialing and grousing, "how I got that cross-bearing through and can't get another squeak out of Curtis was a little shocked by the hatred that gleamed in Androka's with this radio silence?" A far-away look came into Androka's eyes. He did not seem to hear Curtis said: "I understand." "And if the Nazi agents in America knew of the islet from which my zone of silence is projected—" Androka paused, his head tilted to one side, as if he were listening to something— On deck, there was shouting and commotion. Curtis rushed out, pulling picked up, and was being relayed all over the ship. The words struck on Curtis' ears with a note of impending tragedy. "Breakers ahead!" at the end of a swing or smacked against something solid. Curtis felt Nelson's hand grip his shoulder, as he put his lips close to his ear and shouted: "You must have been right, sir, and the radio bearings and my reckoning wrong. We've hit that reef a terrific smack. I'm afraid we're gored!" "Get out the collision mat!" Curtis ordered. "We ought to be able to keep her up!" And then he became aware of a deadly stillness. A vast wall of silence enveloped the entire cruiser. Looking over the side, he could no longer see the waves that a few minutes before had beaten savagely against the ship. The Comerford was shrouded in a huge pall of yellowish-gray mist, and more of it was coming up from below—from ventilators and hatchways and themselves struck numb and helpless by a gas that had been flooded into the inner compartments of their strongholds. explanations— The vapor clouds that enveloped the Comerford shroud of mist and steadied it, so that the cruiser would not be completely at the mercy of the wind and the waves. Curtis heard the anchor let down, as if by invisible hands, the chain screaming and flailing its clanking way through the hawse hole. Then he was completely walled in by the yellowish-gray mist. He felt his senses swimming. Voices droned all around him in mumbling confusion—guttural voices " the other was "convoy." But gradually his eardrums began to throb, as if someone were pounding on them from the inside. He couldn't get his breath gas mask. Nelson spoke in a low tone, his lips close to Bradford's ear. "It worked, Joe!" "I'd rather get along without Androka, if we could!" Nelson muttered. Androka had brought aboard the "The professor's in his glory!" Nelson remarked to Kommander Brandt. "Funny thing about him," Bradford put in, "is that his inventions work. That zone of silence cut us off completely." Kommander Brandt nodded. "Goodt! But you got your message giving your bearings—the wrong ones?" "Yes," Nelson said. "That came through all right. And won't Curtis have a time explaining it!" "Hereafter," Brandt said solemnly, "the zone of silence vill be projected from the Comerford Androka's vich vill be even more useful vhen ve come to cut the "What's the idea?" is taking over." "Can we trust Androka?" Nelson asked, with a sudden note of suspicion "Yes," Brandt assured him. "Of all men—we can trust Androka!" foreigners whom it chooses as its agents," Brandt pointed out. "Androka his daughter and the others will suffer. Androka's loyalty is assured!" room that served as Androka's laboratory and workshop. to rid the below-decks atmosphere of the lethal gas that had overcome the Comerford's very purpose. The pieces of the picture fitted together like a jigsaw puzzle—Androka's zone of silence the bearings given by radio Navigating Officer Nelson's queer conduct. They were all part of a

<question>:
What is Androka trying to make?

<options>:
A A zone of silence that is intended to stop Axis economic flow.
B A zone of silence that is deadly to all who pass through it.
C A zone of silence that will stop Americans from being able to radio Europe.
D A zone of silence that stops all radio signals that attempt to penetrate it.

<answer>:

D