表法猜测的句型：
(1) must have done sth 一定做过某事 否定形式：can't have done
例：She must have come here last night. 她一定是昨晚来的。
She can't have gone there她不可能到那儿去。
(2) may have done sth可能做过某事否定形式：may not have done
例：Philip may have been hurt seriously in the car accident.
Philip 可能在这次车祸中伤得很严重。
(3) might have done sth 或许做过某事 否定形式: might not have done
例：She might have known what the bottle contained.
她或许知道这个瓶子里装的是什么。
(4) should have done sth 估计已经做了某事
否定形式：should not have done 例：She should have arrived in her office by now.她此刻估计已经到达办公室了。