The astronaut did many experiments in the spaceship,            great help for knowing more about space.

A．which we think it is

B．which we think is of

C．of which we think is

D．we think which is of

所有的政策都不是从天上掉下来的，因而几乎所有的始作俑者其经历都充满着艰辛。这句话强调的是( )

A．所有的政策法规都是人制定的

B．开创者都不可避免地会碰到许多困难

C．法规制定者必须具备充分的才智和坚强的毅力

D．制定新的法规是一项创造性的工作