京九线的起止点是( )
A:北京-九江
B:北京-九华山
C:北京-九龙
D:北京-上海
John: What do you do on Sundays?
Tom: I read books and watch TV. What do you do on Sundays?
John: I do my homework . What about you, Mary?
Mary: I clean my room and watch TV.
John: You're helpful.
如图表示平行凸透镜的主光轴的两束光从左边入射凸透镜,F是凸透镜的焦点,请在图中画出这两束光通过凸透镜后的折射光线 。