能够产生周皮的形成层为（）。A、维管形成层 B、木栓形成层 C、副形成层 D、原形成层

__________ his work was still as it had been?

A．It was why that

B．Why is that

C．It is why that

D．Why was it that

成年男性体液量占体重的比例为（）

A.30％

B.45％

C.50％

D.60％

E.75％

既舒筋活络，又化湿和胃的药是

A．独活
B．秦艽
C．木瓜
D．羌活
E．灵仙

线路台账由哪些人员来维护？

光纤的色散主要有（）、（）、（）三种。