has become a problem 与 has became a problem 的区别~

has become a problem 与 has became a problem 的区别~ A generation gap has become a serious problem Exercise: wasting has become a serious problem in the presen today pollution has become a seriously problem on earth. Nowadays(overpopulation)has become a problem we have to face It has become a serious problem百度翻译中文 A generation gap has become a serious problem关于这的英语完形填空 maxthon has encountered a problem A generous gap has become a serious problem.I read a r______ A generation gap has become a serious problem.l read a英语短文翻译 英语翻译a generous gap has become a serious problem.i read a rep 英语翻译A generous gap(代沟) has become a serious problem.I read a