OG 10th 13 请指点!

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 further. 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?

答案C: The machine-tool industry encountered difficulty in obtaining governmental protection against imports on grounds other than defense

整一个没读明白!只知道machine-tool industry和import quotas是有关系的,可是具体的逻辑关系是怎样的呢?请大侠们指点指点!!!谢谢~

DDA说如果制造缩水的话会导致美国的国防，在DD把安全的问题和进口限额联系以前，机器制造业在请愿书中提到了进口配额。

就是说是及其制造业的请愿书导致了进口配额