活塞在上下止点处不偏缸，而在行程中部偏缸最大，其原因是（）。
参考答案：连杆扭曲
—Peter, hurry up! You _____ on the phone.
—Oh, I ______. Thank you. [ ]
A. are being wanted; will come
B. are wanted; am coming
C. want, come
D. will be wanted; should come
大乐律学家荀勖是（）时期的。
A.三国
B.东汉
C.晋
D.西汉
