— Have you seen the film called The trouble with Teenagers?
—Yes, but I don't think it is worth _______.
A:seeing it
B:seeing
C:watching it
D:to watch
根据达尔文的自然选择学说,下列关于长颈鹿进化过程的解释,正确的是( )
①长颈鹿的祖先有的颈长,有的颈短
②在缺乏青草的环境中,颈长的长颈鹿能吃到高处的树叶而活下来
③逐代选择,长颈的变异逐代积累形成长颈鹿
④通过生存斗争,颈长的个体生存.
点A(2,﹣3)关于原点对称的点的坐标是( )