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

<passage>:
And still the machines sputtered. Back at the plant rumor had it that the machines were permanently gutted, and that the plant could never go back into production. Conflicting scuttlebutt suggested that persons high in uniondom had perpetrated the crisis deliberately, bullying Management into the strike for the sole purpose of cutting current dividends and selling stock to themselves cheaply. The rumors grew easier and easier to believe. The workers came to the plants in business suits, it was true, and lounged in the tottering. Production lines slowed. There were daily brawls on the plant floor, in the lounge and locker rooms. Workers began joking about the trash cans "Well? Speak up! What's the beef this time?" the last run of orders we sent out came back because nobody the strike broken in another few hours. Tell them anything." forth in front of the spokesmen for the striking managers. "The board meeting," Walter said gently. "That'll be enough for us." The union boss swore and slammed his fist on the desk. "Walk out in front of those men after what you've done? You're fools! Well, I've given you your chance. You'll get your board to say about it, this one will end with a massacre." The meeting was held in a huge auditorium in the Robling administration building. Since every member of the union owned stock in the company, every member had the right to the men. The solution had been simple, if a trifle ungainly. Everyone who owned stock in Robling Titanium was automatically could have been worse. They might have fired him like poor desire in mind, my friends, to starve you all, and to destroy your company and your jobs. To every appeal they heartlessly refused to divulge the key to the lock-in. And now this man—the ringleader who keeps the key word buried in secrecy—has "What have you been doing lately? Sabotaging the production line?" "What's the trouble now?" the temerity to ask an audience with you. You're angry men receiver. His grin spread unpleasantly from ear to ear. jaws sagging, eyes wide, hardly believing their ears. In the instant of silence as the factory whistle died away, Walter grabbed the microphone. "You want the code word to start the machines again? I'll give it to you before I sit down!" you the code word, and we ask nothing in return but that you listen for sixty seconds." He glanced back at Torkleson, and then out to the crowd. "You men here are an all day?" the ones who have fought moderation right down to the last ditch. You know whom I mean. You know who's grown richer and richer since the switchover. Throw him out, and you too Walter reddened. "He organizes the work of the plant, establishes haven't met a production schedule in over two years. No plant the men." "Nothing's wrong with the men—if they'd only work. But they come in when they please, and leave when they please, and spend half their time changing and the other half on Koffee-Kup. No company could survive this. But that's only knew what the White list meant. No job, anywhere, ever, in management. No chance, ever, to join a union. No more house, no more weekly pay envelope. He spread his hands deteriorate day by day. Now they blamed him, and threatened his job, and he was helpless to do anything about it. He stared at the machines, clicking busily against the wall. It was a repugnant idea. But there was one thing they could do that even Torkleson and his fat-jowled crew would understand. They could go on strike. a case of a company's management striking against its own labor. It—it isn't done. Oh, there have been lockouts, but this isn't the same thing at all." Walter nodded. "Well, we couldn't very well lock the men out, they own the plant. We were thinking more of a lock- in sort of thing." He turned to Paul Hendricks and the others. the machines figure production quotas, organize blueprints, prepare distribution lists, test promotion schemes. It would take an office full of managerial experts to handle even a single phase of the work without the machines." The man at the window hissed, and Pendleton quickly snapped out the lights. They sat in darkness, hardly daring to Union Stockholders. All he'd need to do is ask for managers, and a dozen companies would throw them to him on loan. They'd be able to figure out the machine system and take over without losing a day." "Not quite." Walter was grinning. "That's why I spoke of a lock-in. Before we leave, we throw the machines into feedback, every one of them. Lock them into reverberating circuits with a code sequence key. Then all they'll do is buzz and sputter until the feedback is broken with the key. And the key is our secret. It'll tie the Robling office into granny knots, and scabs won't be able to get any more data out of the machines The others nodded. Walter rubbed his hands together. "All right. Tomorrow we work as usual, until the noon whistle. When we go off for lunch, we throw the machines into lock-step. Then we just don't come back. But the big thing is to keep it quiet until the noon whistle." He turned to the lawyer. The news hit the afternoon telecasts the following day. Headlines screamed: MANAGEMENT SABOTAGES ROBLING MACHINES OFFICE STRIKERS THREATEN LABOR ECONOMY ROBLING LOCK-IN CREATES PANDEMONIUM There was a long, indignant statement from Daniel P. violation of management contracts and illegal fouling of managerial the Amalgamated Buttonhole Makers held a mass meeting in protest, demanding that "the instigators of this unprecedented crime be permanently barred from positions in American Industry." In Washington, the nation's economists were more cautious in their views. Yes, it unions, finding themselves oppressed with the administration floated the loan that threw steel to the unions. Oil had followed with hardly a fight, and as the unions began to feel their oats, gradual undercutting of the managerial salaries, the tightening up of inter-union collusion to establish the infamous White list of Recalcitrant Managers. The shift from hourly wage to annual salary for the factory workers, and the change to the other pole for the managerial staff. And then, with creeping malignancy, the hungry howling of the union bosses for more and higher dividends, year after year, moving steadily toward Torkleson was waiting to see the shop steward when he came in next morning. The union boss's office was crowded with TV cameras, newsmen, and puzzled workmen. The floor machines again, or I'll have them in jail so fast—" He turned back to Bailey. "What about the production lines?" The shop steward's face lighted. "They slipped up, there. meeting right now, have to get the workers quieted down a bit. You put the program through, and give those electronics men three more hours to unsnarl this knot, or we throw them out of the union." He started for the door. "What were the blueprints for?" But the machines continued to buzz and sputter. The workers grew restive. From the first day, Towne and Hendricks and all the others had been picketing the plant, until angry crowds of workers had driven them off with shotguns. machinery began tying itself in knots, and the strikers still struck. By the fifth day there was a more serious note. you in jail if you don't start the machines again. They may have you in jail if you do charges were read: "—breach of contract, malicious mischief, sabotage of the company's machines, conspiring to destroy the livelihood of ten thousand workers. Your Honor, we are preparing briefs to prove further that these men have formed a

<question>:
How did the managers shut the plant down for a strike?

<options>:
A By locking all of the workers in the plant
B By cutting the power for the plant
C By sending the production machines into feedback loops
D By locking out all of the workers

<answer>:

C