英语语法问题，(详细详细详细解答) 不要纯答案，要解释.并且指出错误答案为什么错。谢谢 题目如下

1、Greater efforts to increase agricultural production must be made if food shortage_____avoided
A、is to be
B、can be
C、will be
D、has been
2、It____for over a month and the down pour had damaged many houses
A、rained heavily
B、had been raining cats and dogs
C、has been raining heavily
D、has rained cats and dogs

A。除了A没有表将来或者目的的。

B。后面那句是时间标准，已经是过去式了，只能选过去的过去，had done

第二题正确答案是D