OG13 DT SC 38 that从句和and

yilian双皮奶

The results of two recent unrelated studies support
the idea that dolphins may share certain cognitive
abilities with humans and great apes; the studies
indicate dolphins as capable of recognizing
themselves in mirrors—an ability that is often
considered a sign of self-awareness—and to grasp
spontaneously the mood or intention of humans.


(A) dolphins as capable of recognizing themselves
in mirrors—an ability that is often considered a
sign of self-awareness—and to grasp
spontaneously
(B) dolphins’ ability to recognize themselves in
mirrors—an ability that is often considered as a
sign of self-awareness—and of spontaneously
grasping
(C) dolphins to be capable of recognizing
themselves in mirrors—an ability that is often
considered a sign of self-awareness—and to
grasp spontaneously
(D) that dolphins have the ability of recognizing
themselves in mirrors—an ability that is often
considered as a sign of self-awareness—and
spontaneously grasping
(E) that dolphins are capable of recognizing
themselves in mirrors—an ability that is often
considered a sign of self-awareness—and of
spontaneously grasping


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对答案没有异议，但是对OG的解释有个疑问：
OG13上说，indicate引导的从句必须有that？但是朗曼字典上表示：indicate (that)，that是可以省略的。为什么这里必须有that呢？还是GMAT要求必须有that？

还有一个问题，关于平行
a sign of...and of...
可不可以a sign of...and ...？
谢谢

chineuro

答案是E？

1. GMAT语法自有一套体系，除了词义和固定搭配以外，建议不要参考其他字典的语法；两者大相径庭。
2. that dolphins are capable of recognizing themselves in mirrors—an ability that is often considered a sign of self-awareness—and of spontaneously grasping
要看对句子结构，这里是be capable of recognizing... and of grasping并列。中间的a sign of 作为插入部分是不和任何其他of并列的。