最近在学新二，发现时态很混乱，同样一篇课文讲过去的事，有的用现在完成时有的用一般过去式。比如新二52课：i have temporarily put my books on the floor……my sister helped me to carry one of my old bookcase up to the stairs.我想问下，都是已经发生的事，为什么前面那句用have put的完成时形态，后面却用helped一般过去式。这样的情况比比皆是。到底要怎么区分？还有第一篇课文，yesterday，i went into a theatre,都说了是昨天了，为什么不用i had gone into a theatre.
