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题目内容
（河北工程技术学院大学英语1）
31、(单选、2.5分)
Companies usually ________ a number of experiments before a new product is launched.
A、practice
B、control
C、carry
D、conduct
Companies usually ________ a number of experiments before a new product is launched.
A、practice
B、control
C、carry
D、conduct
参考答案