由 which引导的定语从句。which指物,在从句中既可作主语,也可作宾语。作宾语时可省略。
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They found an ancient metal tool whose function is still unknown
A. 对
B. 错
guard against是防范
A. 对
B. 错
They turned out ( to be ) successful
A. 对
B. 错
I rejected the idea of England because it was not exciting enough
A. 对
B. 错