e busy with sth忙于某事
固定搭配
给你些例句 更好
You must be very busy with your call.
你一定是忙着应酬吧.
She's busy with some important work.
她正忙于一些重要工作.
be busy(in) doing sth 忙于做某事
He is busy in preparing for the examination.
他忙着准备考试.
with sth.和in doing sth.比较常见
所以选择with