1. 英语语法
  2. 动词的时态
  3. 一般现在时代替过去时

1 )"书上说","报纸上说"等。

例句:

The newspaper says that it's going to be cold tomorrow.

报纸上说明天会很冷的。

2) 叙述往事,使其生动。

例句:

Napoleon's army now advances and the great battle begins.