求教GWD

ken178

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.



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

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

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

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

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

能解释一下这题D错在哪里吗？？？谢谢


加多一题：In 1981 children in the United States
spent an averageof slightly less than two and a half hours a week doinghousehold chores; by 1997 they had spent nearly six hours a week.
A.chores; by 1997 they had spent nearly six hoursa week

B.chores; by 1997 that figure had grown to nearlysix hours a week

C.chores, whereas nearly six hours a week werespent in 1997

D.chores, compared with a figure of nearly six hours a week in 1997

E.chores, that figure growing to nearly six hours a week in 1997

请NN来详细解读一下这题。不是那么明白