与地球自转有关的自然现象是（ ）
A．极昼、极夜
B．四季更替
C．昼夜更替
D．昼夜长短变化
答案：C
简述教师的职业道德和职业情感。
I didn't go to the football match because the ticket was______expensive for me.
A．very much
B．so much
C．for too
D．a lot of
