Wind and rain continually hit against the surface of the Earth, （） large rocks into smaller and smaller particle.

单项选择题The stubborn young man did not follow the advice that he （）on his behavior since he refused to believe he had done anything wrong.

A．reflect
B．had reflected
C．would reflect
D．must reflect

单项选择题Variables such as individual and corporate behavior （）nearly impossible for economists to forecast economic trends with precision.

A．make
B．to make it
C．it makes
D．make it