I could ask you could ask he could ask we could ask you could ask they could ask
V-ing form
I could be asking you could be asking he could be asking we could be asking you could be asking they could be asking
Perfect
I could have asked you could have asked he could have asked we could have asked you could have asked they could have asked
V-ing perfect
I could have been asking you could have been asking he could have been asking we could have been asking you could have been asking they could have been asking
Negation
Simple form
I couldn't ask you couldn't ask he couldn't ask we couldn't ask you couldn't ask they couldn't ask
V-ing form
I couldn't be asking you couldn't be asking he couldn't be asking we couldn't be asking you couldn't be asking they couldn't be asking
Perfect
I couldn't have asked you couldn't have asked he couldn't have asked we couldn't have asked you couldn't have asked they couldn't have asked
V-ing perfect
I couldn't have been asking you couldn't have been asking he couldn't have been asking we couldn't have been asking you couldn't have been asking they couldn't have been asking
Interrogative form
Simple form
could I ask? could you ask? could he ask? could we ask? could you ask? could they ask?
V-ing form
could I be asking? could you be asking? could he be asking? could we be asking? could you be asking? could they be asking?
Perfect
could I have asked? could you have asked? could he have asked? could we have asked? could you have asked? could they have asked?
V-ing perfect
could I have been asking? could you have been asking? could he have been asking? could we have been asking? could you have been asking? could they have been asking?
Interro-negative form
Simple form
couldn't I ask? couldn't you ask? couldn't he ask? couldn't we ask? couldn't you ask? couldn't they ask?
V-ing form
couldn't I be asking? couldn't you be asking? couldn't he be asking? couldn't we be asking? couldn't you be asking? couldn't they be asking?
Perfect
couldn't I have asked? couldn't you have asked? couldn't he have asked? couldn't we have asked? couldn't you have asked? couldn't they have asked?
V-ing perfect
couldn't I have been asking? couldn't you have been asking? couldn't he have been asking? couldn't we have been asking? couldn't you have been asking? couldn't they have been asking?