1．表述客观真理和客观存在及自然现象；表示习惯性、经常性的动作，或经常存在的状态。常见的时间状语有：often，usually，always，sometimes，now and then等。
The sun rises in the east and sets in the west.
太阳从东方升起，从西边落下。
My parents live in Hong Kong.They were born there and have never lived anywhere else.
我的父母住在香港。他们在那里出生而且从未在别的地方生活过。
