色多多在线观看播放-色多多在线观看高清免费-色多多在线观看视频-色多多在线看-欧美aaaaa性bbbbb小妇-欧美aaaav免费大片

"Psychology must focus on the utility of mental operations."

Mathematics is not just about numbers, equations, computations, or algorithms: it is about understanding.

困難之中孕育著機遇。

我不相信英雄，但我相信那些做英雄事跡的人。