系动词,比如become可以有过去式,但是可不可以变成is becoming?

系动词,比如become可以有过去式,但是可不可以变成is becoming? become不是系动词么?为什么出来了“is becoming”呢? become作系动词的时候不是没有进行时吗?那It is becoming better中become是什么词? 动词变成过去式有哪些规则? is become 和 is becoming 这两个短语有何区别? her wish is to become a doctor 和 ````becoming ``有什么区别吗? 人教版初中动词变形比如把动词变成单三 现在分词 过去式 过去分词 His wish is to become a scientist为什么不是becoming is becoming和have become什么意思,区别, 关于英语问题我知道系动词后要跟形容词,那可不可以跟副词呢?那系动词的过去式,即be动词的过去式,可以加形容词吗?那可以加 过去式中,be的过去式后面可不可以加动词过去式? 帮我将动词变成过去式,