完全竞争市场条件下，厂商的需求曲线、平均收益曲线、边际收益曲线是重叠的。

Albert Einstein once attributed (把......归因于) the creativity of a famous scientist to the fact that he "never went to school, and therefore kept the rare gift of thinking freely". There is undoubtedly a truth in Einstein’s observation; many artists and geniuses seem to view their schooling as a disadvantage. But such a truth is not a criticism of schools. It is the function of schools to civilize, not to train explorers. The explorer is always a lonely person whether his or her pioneering be in art, music, science, or technology. The creative explorer of unmapped lands shares with tile genius what William James described as the gift for thinking in an unusual way. As schools teach set patterns, they tend to destroy creativity and genius. But if schools could somewhat exist only to cultivate genius, then society would break down. For the social order demands unity and widespread agreement, which r, re destructive to creativity and genius.

Albert Einstein once thought that schools ______.

A．helped develop the creativity of a scientist

B．kept a rare gift for a scientist

C．prevented a scientist from thinking freely

D．contributed a lot to science and technology