1. 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.