请教各位牛人

queenjie

（1）     GWD-23-Q13

Researchers hypothesize that granitic soil is the ideal construction material for the desert tortoise because it is not so hard that it makes burrowing difficult or so soft that it could cause tunnels to collapse.

 

1. so hard that it makes burrowing difficult or so soft that it could cause

2. hard enough to make burrowing difficult or soft enough as to cause

3. so hard as to make burrowing difficult or soft enough so it causes

4. as hard as to make burrowing difficult or as soft as to cause

5. too hard, making burrowing difficult, nor too soft, so as to cause

答案是A,D为什么错

neo1001

D的话， it is not as hard as to make burrowing difficult or....，第一个it明显指代granitic soil

这句是比较，于是意思就是“ to make burrowing difficult 没有 it（指代soil）这么难/硬”，怎么解释都不通。