has become。因为has后面要接动词的过去分词形式，动词become的过去分词是become，became是动词become的过去式。become作及物动词时意为“成为；变得；变成”，第三人称单数变化是becomes；现在分词形式是becoming。
has become的例句The environment has become a very hot issue.
环境已成为很热门的话题。
The Internet has become part of everyday life.
互联网已成为日常生活的一部分。
The new office block has become an expensive white elephant.
这座新办公大楼成了昂贵的摆设。
May Day has become a venerable institution
五朔节已经变成一个神圣庄严的传统节日。
The programme has become a firm favourite with young people.
这个节目已着实赢得了年轻人的喜爱。
become相关短语become rich疾速致富；迅速致富；火速致富；神速致富
become extinct灭绝；变坏；绝种
has become成长为；已经成为；已变成；已经变成
become conscious醒悟；恢复知觉
become weak手发软；变得萎靡不振；倦怠；变弱
become invalid作废；成为无效；变得无效；这药已失效了
