He said he had nothing ______ to say.
A. further
B. farther
C. less
D. any most
He said he had ______ to tell the manager.
A. important something
B. important nothing
C. anything important
D. something important
He can swim______.
A. as fast as Tom, if not faster than
B. as fast as, if not faster than, Tom
C. as fast, if not faster, as Tom
D. faster, if not as fast as Tom
菌种衰退的原因可能是
A. 基因突变
B. 连续传代
C. 不适应的培养条件
D. 不适宜的保藏条件
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