人类语言和所谓动物语言的关键区别在于，人类语言具有（ ）
A．符号的离散性
B．发音的多样性
C．发音的复杂性
D．系统的相对封闭性
参考答案：A
We go to school from Monday to Friday, and go to ___ cinema on Saturday or Sunday.
A．a
B．the
C．an
D．/
The old engineer's eyes still shone bright in the wrinkled brown face and his step as he came across the room
was _____, though slow. [ ]
A. shaky
B. heavy
C. casual
D. steady
