though he is young ,___knows a lot A yet he B however he 为什么不能选b?

问题描述:

though he is young ,___knows a lot A yet he B however he 为什么不能选b?

A yet 虽然有但是的意思 它既可以做连词也可作副词可以和though连用
而however是副词 必须有逗号给开