modal+have

描述後悔的事，過去應該怎樣

• I should have studied something more practical when I was in college.
• I shouldn't have waited so long to choose a major.
• I should have been more conscientious when I was young.
• I shouldn't have been argumetative with my boss.
• I shouldn't have been completely rebellious when I was a student.

描述假設的情況

• If I'd been more ambitious in colledge, I could have learned another language.
• If I hadn't wasted so much money last year, I would have my own apartment.
• Id I'd listened my parents, I would have made more pragmatic decisions.
• If I'd been more active , I wouldn't be overweight.

猜測發生什麼事

幾乎確定得猜測

• She must have left already.
• She must not have turned on her cell phone.

有可能的猜測

• She may/might have forgotten the time.
• She may/might not have remembered the time.
• Her car could have borken down.
• She couldn't have been at home.

給建議、勸告對方

• You should have called her on the phone.
• She shouldn't have kept your notes this long.
• You could have been more understanding.
• I wouldn't have lent my notes to her this week before a test.