unit 2
cleaned    (clean 的过去式)打扫
stayed    (stay 的过去式)停留；待
washed   (wash的过去式)看
watched   (watch 的过去式)看
had   (have 的过去式)患病；得病
had a cold   感冒
slept   （sleep的过去式）睡觉
read   (read的过去式)读
saw   (see的过去式)看见
last    最近的；上一个的
yesterday    昨天
before    在……之前

