采区水仓的有效容量有什么要求？
参考答案：采区水仓的有效容量应当能容纳4h的采区正常涌水量。
Mary is sure to come for dinner if she ________ time this evening. [ ]
A. has
B. will have
C. had
D. is having
简述饲料中添加酶制剂的必要性与可能性。
