977.When changing lanes,a driver should use his turning signal to let other drivers know _______.
A.he is entering which lane
B.which lane he is entering
C.is he entering which lane
D.which lane is he entering
978.It is uncertain _____ side effect the medicine will bring about, although about two thousand patients have taken it.
A.that
B.what
C.how
D.whether
977.答案是B;此处which引导的从句作know的宾语，务必注意句子应用陈述语序。
978.答案是B;此处what side effect充当bring about的宾语。
