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 could not ask you could not ask he could not ask we could not ask you could not ask they could not ask
V-ing form
I could not be asking you could not be asking he could not be asking we could not be asking you could not be asking they could not be asking
Perfect
I could not have asked you could not have asked he could not have asked we could not have asked you could not have asked they could not have asked
V-ing perfect
I could not have been asking you could not have been asking he could not have been asking we could not have been asking you could not have been asking they could not 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
could I not ask? could you not ask? could he not ask? could we not ask? could you not ask? could they not ask?
V-ing form
could I not be asking? could you not be asking? could he not be asking? could we not be asking? could you not be asking? could they not be asking?
Perfect
could I not have asked? could you not have asked? could he not have asked? could we not have asked? could you not have asked? could they not have asked?
V-ing perfect
could I not have been asking? could you not have been asking? could he not have been asking? could we not have been asking? could you not have been asking? could they not have been asking?