Busy ___he is,he always finds time for sports.A.as B.although为什么although在这里不对呢?

这是个部分倒转,基本句型是 形容词+as +主语+be
如果同although，这个句子就只能这样了：Although he is busy,he always finds time for sports.

如果把busy位于句首，可以用as或though，但是不能用although.
如果联系词放句首的时候，就可以用although了。
还有要注意的是，在这种句式中，如果是单数名词位于句首，名词不能加冠词，例如：
Child as he is, he runs fast.
尽管他还是一个孩子，他跑的很快。

although 用在前面
although he is busy......

although必须在句首！

although引导的让步状语从句不用倒装语序,though引导的让步状语从句可用也可以不用倒装语序,as引导的让步状语从句一定要用倒装语序.
在这句话中,如果用although的话,要这样表达：Although he is busy,he always finds time for sports.
要是用though的话,这样表达：Busy though he is,he always finds time for sports或Though he is busy,he always finds time for sports.
要是用as表达的话,这样：Busy as he is,he always finds time for sports.

as可以倒装，although不可以。