he _(write )the letter to his pen pal since 9 am .用括号里所给词的恰当形式填空 ,并说明理由.
问题描述：
he _(write )the letter to his pen pal since 9 am .用括号里所给词的恰当形式填空 ,并说明理由.
答
has been writing
他从上午九点起就一直在给他的笔友写信.
因为since 9 am 表明从过去一个时间点持续到现在,所以用现在完成进行时.
请及时采纳,多谢!