1） 时间副词 如：ago, before, already, just, now, early, late, finally, tomorrow等.
2） 地点副词 如：here, there, near, around, in, out, up, down, back, away, outside等.
3） 方式副词 如：carefully, angrily, badly, calmly, loudly, quickly, politely, nervously等.
4） 程度副词 如：almost, nearly, much, greatly, a bit, a little, hardly, so, very等.
