1. Researchers at Cornell University have demonstrated that homing pigeons can sense changes in the earth’s magnetic field, see light waves that people cannot see, detect low-frequency sounds from miles away, sense changes in air pressure, and can identify familiar odors.

(A) sense changes in air pressure, and can identify familiar odors

(B) can sense changes in air pressure, and can identify familiar odors

(C) sense changes in air pressure, and identify familiar odors

(D) air pressure changes can be sensed, and familiar odors identified（C）

(E) air pressure changes are sensed, and familiar odors identified

请教这里before 的用法，谢谢

这题还用说吗，考平行结构，C啊。

请教before的用法？？这题没有before这个字啊，什么意思？