the boy offten gives a satisfactory answer to the teather's question,just a mintue

问题描述:

the boy offten gives a satisfactory answer to the teather's question,just a mintue
在上面的句子中,用-ing好还是用-ing的完成式.
A thinking B having thought
just前有一空,我不知用那中形式 为什么用完成时

B
offten 是什么