一个五边形共有______条对角线．
n边形共有n(n-3)2条对角线，
∴五边形共有5(5-3)2=5条对角线．
蝗虫的视觉器官是（）.
A眼睛
B眼点
C复眼
D单眼
The director gave me a better offer than( )．
A．that of John’s
B．John’s
C．he gave John
D．those of John
