All the players in the football team must be (trained)five time a week.
问题描述：
All the players in the football team must be (trained)five time a week.
这里为什么要用trained
答
train在这里做及物动词,这句话可假设是教练说的,队员要在我的指导下训练,所以是be trained,如果是队员自己训练,可以用train,不及物动词用法