I'll play with you when I am free.------------I'll play with you when I 'm not busy.I'll play with you when I am free. I'll play with you when I____________.(有且只有两个空格I'll play with you when I am free. I'll play with you when I____________.(有且只有两个空格 (have time)可否填not busy .为什么？谢谢！不能用not busy，因为I是主语，后面必须要有动词才为句子，而busy是形容词，用在主语后面它前面还必须要有be动词，组成be busy。再因为你这个问题只给2个空，所以可以换成have time,和be free 是同义词，而be busy 则和前面2个成反义词。