管子下沟时应吊放在管沟内（）。
A.任意位置
B.靠右侧位置
C.中心线位置
D.靠左侧位置
参考答案：C
We were talking about Tom _____ he came in. [ ]
A. were
B. while
C. when
D. during
“言语”的语音形式中包含了（）个音素。
