i think in D, we are incorrectly comparing soil with hardness which is incorrect. it refers to soil....as hard as to make burrowing difficult or as soft as to cause
A, is correct because it refers to soil and soil is not so hard or so soft. we do not repeat not.
hope this helps.
C. is out because hardness is compared with burrowing.
Researchers hypothesize that granitic soil is the ideal construction material for the desert tortoise because it is notso hard that it makes burrowing difficult or so soft that it could cause
...
A, is correct because it refers to soil and soil is not so hard or so soft. we do not repeat not.
hope this helps.
C. is out because hardness is compared with burrowing.
jzchina wrote:
Researchers hypothesize that granitic soil is the ideal construction material for the desert tortoise because it is notso hard that it makes burrowing difficult or so soft that it could cause
...
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