在对过去发生的事件进行描述时,过去的动作用过去时,但有些描写则仍用一般时,如：
I went to the People's Park with my friends yesterday.The weather was fine.The flowers there are beautiful.There's a lake in the middle of the park.We had a picnic by the lake.
段落中所有发生在昨天的事都用过去时,但对花、湖的描写仍用一般现在时.明白了吗?