I could omit you could omit he could omit we could omit you could omit they could omit
V-ing form
I could be omitting you could be omitting he could be omitting we could be omitting you could be omitting they could be omitting
Perfect
I could have omitted you could have omitted he could have omitted we could have omitted you could have omitted they could have omitted
V-ing perfect
I could have been omitting you could have been omitting he could have been omitting we could have been omitting you could have been omitting they could have been omitting
Negation
Simple form
I could not omit you could not omit he could not omit we could not omit you could not omit they could not omit
V-ing form
I could not be omitting you could not be omitting he could not be omitting we could not be omitting you could not be omitting they could not be omitting
Perfect
I could not have omitted you could not have omitted he could not have omitted we could not have omitted you could not have omitted they could not have omitted
V-ing perfect
I could not have been omitting you could not have been omitting he could not have been omitting we could not have been omitting you could not have been omitting they could not have been omitting
Interrogative form
Simple form
could I omit? could you omit? could he omit? could we omit? could you omit? could they omit?
V-ing form
could I be omitting? could you be omitting? could he be omitting? could we be omitting? could you be omitting? could they be omitting?
Perfect
could I have omitted? could you have omitted? could he have omitted? could we have omitted? could you have omitted? could they have omitted?
V-ing perfect
could I have been omitting? could you have been omitting? could he have been omitting? could we have been omitting? could you have been omitting? could they have been omitting?
Interro-negative form
Simple form
could I not omit? could you not omit? could he not omit? could we not omit? could you not omit? could they not omit?
V-ing form
could I not be omitting? could you not be omitting? could he not be omitting? could we not be omitting? could you not be omitting? could they not be omitting?
Perfect
could I not have omitted? could you not have omitted? could he not have omitted? could we not have omitted? could you not have omitted? could they not have omitted?
V-ing perfect
could I not have been omitting? could you not have been omitting? could he not have been omitting? could we not have been omitting? could you not have been omitting? could they not have been omitting?