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

<passage>:
feet, then turned and positioned himself, some five feet behind the table, on a line of sight with the airlock. "I can see it," he said. "It's getting redder. It's ... it's ... melting, yes. Melting down at the bottom a little. Now it's falling over to one side and laying on the air tank. The air tank is getting red, too. I'm afraid ... it's weakening it.... Redder. Oh, oh." Major Winship, after receiving the message, discussed precautions with the three other Americans. Next morning, before the sunlight exploded, the four of them donned their space suits and went and sat outside the dome, waiting. The sun rose with its bright, silent clap of radiance. Black pools of shadows lay in harsh contrast, their edges drawn with geometric precision. bright flare from inside the dome, and a great, silent tongue of flame lashed through the airlock and rolled across the lunar surface. The table was sent tumbling. The flame was gone almost instantly. Gagarin. "Will you please request the general to keep us informed on the progress of the countdown?" He was still floating toward the ground when there was an incredibly "Is Pinov," came the reply. "Help?" Progress. When—boom?" "There went the air," Capt. Lawler commented. "When?" Americans. "How are we going to know when it's over?" "Let's all go in," said the fourth American, Capt. Lawler. "It's probably over by now." channel. "Base Gagarin? Base Gagarin?" "Is Pinov. Help?" " is it," he said. "I'm going in." "Let's all—" "The static level hasn't gone up much, if at all." "Maybe," Lt. Chandler said, "it's buried too deep." "Maybe so," Major Winship said. "But we can't have the dome fall down around all our ears." He stood. "Whew! You guys stay put." He crossed with the floating moon-motion to the airlock and entered, closing the door behind him. The darkness slowly filled with air, and the temperature inside the suit declined steadily. At the proper moment "It's—" "I guess it's over," said Major Winship, getting to his feet. "Wait a "I guess I was just—" Major Winship began. "Oh, hell! We're losing pressure. Where's the markers?" sprung a little, and I can't get it to conform over the rivet heads." There was a splatter of static. "Major Winship! Hello! Hello, hello, hello. You A Okay?" "This is Major Winship." "Right here." Major Winship looked at the microphone. "Well, I'll just report and—" "That's right, isn't it." They huddled over the instruction sheet. service." Major Winship said dryly, "Never mind. I notice it hardens on contact with air." air must already have leaked into this one. It's hard as a rock. A gorilla couldn't extrude it." "That's that," Major Winship said. "There's nothing for it but to yell help." II Capt. Lawler and Lt. Chandler took the land car to Base Gagarin. The cursed twice during the operation. "I'd hate to live in this thing for any period." "I think these suits are one thing we've got over the Russians," Major "They've got the power-plants for it." "Do you think he did that deliberately?" Major Winship asked. "I think he's trying to force us off. I think he hoped for the quake. Gagarin's built to take it, I'll say that. Looks like it, anyhow. You don't suppose they planned this all along? Even if they didn't, they sure got "That's the thing. That's the thing that gripes me, know what I mean? They roused Earth. "This is Major Charles Winship, Commanding Officer, Freedom 19, the American moonbase." "This is the Cape. Come in, Major Winship." "Is everything all right?" Major Winship was squirming nervously, obviously perturbed. "What's wrong?" came the worried question. In the background, he heard large to the other. Major Winship made a strangling motion and reached for his throat. One "We're here," Major Winship said. Soviet Union fired an underground atomic device for the ostensible purpose of investigating the composition of the lunar mass by means of seismic analysis of the resultant shock waves. This was done in spite of American warnings that such a disturbance might release accumulated stresses in the long undisturbed satellite, and was done in the face of vigorous American protests." "These protests have proved well founded," Major Winship continued. "Immediately following the detonation, Freedom 19 was called on to withstand a moderately severe shifting of the Lunar surface. No personnel were injured and there was no equipment damage." flicked the appropriate chest button and nodded in appreciation. "However," he continued, "we did experience a minor leak in the dome, which is presently being repaired." "The Soviet Union," came the reply, "has reported the disturbance and "It can wait until later. Send it by mail for all I care. Vacuum has destroyed our organic air reconditioner. We have approximately three weeks of emergency air. However, Base Gagarin reports no damage, so that, in the event we exhaust our air, we will be able to obtain the necessary replacement." the conversation a tone of deliberation. Methodically, Capt. Wilkins set about disconnecting the major from the The airlock to Freedom 19 was open. "What is that ?" asked Major to prevent a purely scientific experiment, the results of which will be published in the technical press for the good of everybody. I'll bet!" "The question is," Capt. Lawler said, "'How are we going to mix it?' forth through the airlock. At that time, it was apparent the table was interposing itself. Lt. Chandler tried to dismantle the table. "Damn these suits," he said. that." "I don't think this is the way to do it," Major Winship said. "Let's the main air-supply tank and the transmitter. They were all perspiring. "It's not the weight, it's the mass," said Capt. Wilkins brightly. "The hell it isn't the weight," said Lt. Chandler. "That's heavy." "With my reefer out," said Major Winship, "I'm the one it's rough on." He shook perspiration out of his eyes. "They should figure a way to get a mop in here, or a towel, or a sponge, or something. I'll bet you've forgotten how much sweat stings in the eyes." "It's the salt." "Speaking of salt. I wish I had some salt tablets," Major Winship said. "I've never sweat so much since basic." "Want to bet Finogenov hasn't got a bushel of them?" "No!" Major Winship snapped. "Now what, Skip? The instructions aren't in English." "With what?" asked Major Winship. just a little bit, Finogenov said. An hour or so, maybe." "I hope this doesn't set on exposure to air." "No," Capt. Lawler said. "It sets by some kind of chemical action. General Finogenov wasn't sure of the English name for it. Some kind of is "Out! Out!" He and the Major reached the airlock at the same time and became temporarily engaged with each other. Movement was somewhat ungainly in the space suits under the best of conditions, and now, with the necessity for speed, was doubly so. The other two crashed into them from behind, and they spewed forth from the dome in a tangle of arms and legs.

<question>:
What is the main conflict at the start?

<options>:
A The American astronauts can't get in contact with anyone who speaks English.
B Winship's reefer stops working properly.
C The Americans are unable to tell when the scheduled explosion is going off.
D The harsh sunlight is making the astronauts perspire.

<answer>:

C