13。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 machie-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 concerned with the effects of foreign competition on the machine-tool industry
C the machine-tool industry encountered difficulty in obtaining governmental 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 government programs have been designed which will enable domestice machine-tool manufacturing firms to compete successfully with foreign toolmakrs.
俺后来反复看题理解了og的答案，但是关于正确选项c本身，后半截没看懂，imports on grounds other than defense啥意思？
48 A researcher discovered that people who have low levels of immune-system activity tend to score much lower on tests of mental health than do people with normal or high immune-system activity. The researcher concluded from this experiment that the immune system protects against mental illness as well as against physical disease.
the reseacher's conclusion depends on which of the following assumptions?
A high immune-system activity protects against mental illness better than normal immune-system activity does.
B mental illness is similar to physical disease in its effects on body systems.
C people with high immune-system activity cannot develp mental illness.
D mental illness does not cause people's immune-system activity to decrease.
E psychological treatment of mental illness is not as effective as is medical treatment.
og给的答案是D，我的答案是B，请各位高人指点。 | 
