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题目内容
（大连工业大学-大学英语4）
(单选题) The book proved to be very reliable and so was very ( ) to him in his research.(本题3.0分)
A、 useless
B、 invaluable
C、 negligible
D、 precious
A、 useless
B、 invaluable
C、 negligible
D、 precious
参考答案