求教补充教材177 题

Believed to originate from a small area on their foreheads, elephants emit low-frequency sounds that may be used as a " secret language" to communicate with other members of the herds.

(A) Believed to originate from a small area on their foreheads, elephants emit low-frequency sounds aht may be used

(B)Elephants emit low-requency sounds that are believed to originate from a small area on their foreheads, and they may use this

(C)Elephants emit low-requency sounds that are believed to originate from a small area on their foreheads, that they may use

(D)Originating, it is believed, from a small area on their foreheads;elephants emit low-frequency sounds they may use

(E)Originating, it is believed, from a small area on their foreheads, low-frequency sounds are emitted by elephants that may be used

Key (C)

不明白 that they may use 在这里是定语从句？ 前面有逗号，可以用that 引导吗？

不明白你的版本为何和我的不同,

这是原题, C就可以理解了,中间是插入语

  Believed to originate from a small area on their foreheads, elephants emit low-frequency sounds that may be used as a secret language to communicate with other members of the herd.

(A) Believed to originate from a small area on their foreheads, elephants emit low-frequency sounds that may be used

(B) Elephants emit low-frequency sounds that are believed to originate from a small area on their foreheads, and they may use this

(C) Elephants emit low-frequency sounds, believed to originate from a small area on their foreheads, that they may use

(D) Originating, it is believed, from a small area on their foreheads; elephants emit low-frequency sounds they may use（C）

(E) Originating, it is believed, from a small area on their foreheads, low-frequency sounds are emitted by elephants that may be used

thax  a lot.