1. 这本小说我已读了三遍。

    误.I’ve read the novel the third time:

    正.I’ve read the novel a third time:

    析.要表示数量或序数的增加,在序数词前用不定冠词。又如：He saw a second plane: 他又看到了第二架飞机。

    2.他在公共汽车后面追，并追上了。

    误.He ran after the bus, and could catch it:

    正.He ran after the bus, and was able to catch it:

    析.表示过去特定情况下的能力，可用 was (were) able to 而不能用 could ......