The standardized educational or psychological tests are widely used to aid in selecting, classifying, assigning, or promoting students, employees and military personnel. But they have been the target of recent attacks in books, magazines, and even in Congress. The target is wrong, for in attacking the tests, critics divert attention from the fault that lies with ill-informed or incompetent users. The tests themselves are merely tools, with characteristics that can be measured with reasonable precision under specified conditions. Whether the results will be valuable, meaningless, or even misleading depends partly upon the tools themselves but largely upon the user.

泥炮发生故障时，严禁将手伸进（）内。

A、炮膛

B、炮身

C、泥炮

D、开口机