贴现和再贴现市场的参加者主要有（）。 A.商业票据的持有者 B.商业银行 C.中央银

— Mike, what did our monitor say just now?

— Every boy and every girl as well as the teachers who _____ to visit the museum _____ asked to be at

   the school gate before 6:30 in the morning. [ ]

A. is ; is

B. are; are

C. is; are

D. are; is

VD/VT在成人和小儿大致相同，正确的是（）。

A.0.4

B.0.2

C.0.3

D.0.6

E.0.5

选煤用的最多的重介质加重材料是（）。

A、砂子

B、黄泥

C、磁铁矿

D、氯化锌

There have been many（）in their marriage but they still love each other.

A.ups and downs

B.from head to toe

C.time and again

D.over and over

千家万户养蚕时的蚕种怎么会统一孵化的？