关于twice的用法

sarahstany

To meet the rapidly rising marketdemand for fish and seafood, suppliers are growing fish twice as fast as their natural growth rate, cutting their feedallotment by nearly half and raising them on special diets.

(A) their natural growth rate, cutting their feed allotment
(B) their natural growth rate,their feed allotment cut
(C) growing them naturally, cutting their feed allotment
(D) they grow naturally, cutting their feed allotment
(E) they grow naturally, with their feed allotment cut

我选D

sarahstany

查了章振邦语法,

i.  x times(twice) + the + n.

ii.  x times adj. (比较形式) than

iii.  x times as adj. as    注意里面的adj要和前面的名词匹配

   A do x times as adj. … x as B do

iv.  x times + what 分句  

v.                   x-fold

vi.                 double, triple, quadruple, quintuple,

第5种有人在GMAT里见过么?
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我上次考试遇到一题，有2个选项的纠结：
1   ...equal to twice that ...
2  ...twofold as that....

twice是adv副词，第1种equal to twice用法错误, 也罗嗦。
应该是第2种 twofold as that 更好。twofold 是adv &adj均可。