OG-13题

Defense Department analysts worry that the ability of the United States to wage a prolonged war would be seriously endangered if the machine-tool manufacturing base shrinks furthur. Before the Defense Department publicly connected this security issue with the import quota issue, however, the machine-tool industry raised the national security issue in its petition for import quotas.

Which of the following, if true, contributes most to an explanation of the machine-tool industry's raising the issue above regarding national security?

(A) When the aircraft industries retooled, they provided a large amount of work for tool builders.
(B) The Defense Department is only marginally concered with the effects of foreign competition on the machine-tool industry.
(C) The machine-tool industry encountered difficulty in obtaining govermental protection against imports on grounds other than defense.
(D) A few weapons important for defense consist of parts that do not require extensive machining.
(E) Several federal goverment programs have been designed which will enable domestic machine-tool manufacturing firms to compete successfully with foreign toolmakers.

答案为什么是C, 由谁能给翻译一下题干? 谢谢!