Perfect modals

1- could have + past participle

تعني القدرة والإمكانية في الزمن الماضي.)كان من الممكن أن ..لكن لم ...)

 Why did they wait for the doctor?

  They could have given the boy first aid.

2- should have + past participle

تعني النصيحة المتأخرة ( أي كان يجب عليك )

A: I failed my test.

B: You should have studied hard for the test.

   

3- must have + past participle

تعني انه كان يجب (للضرورة والاستنتاج)مثبت

·        Where are my keys?

 You must have lost them at home.

للاستنتاج المنفي نستعمل couldn’t have +p.p