He used to sit for hours _____nothing in the boat ,选doing,是不是省略but,即He used to sit for hours but doing nothing in the boat 他过去常常在船上坐上数个小时,什么事情也不做.还是怎么回事,要讲解阿,别光说,进行时表示伴随动作,听不懂,英语强者,