单项选择题
It is useful to science（）the earth as an object in space.
A.to consider B.which considers C.considers D.the consideration of
单项选择题 We must（）that the experiment is controlled as rigidly as possible.
单项选择题 Be careful,（）you'll fall down.
单项选择题 （）the movie I would have finished my paper last Sunday.
