I could omit you could omit she could omit we could omit you could omit they could omit
V-ing form
I could be omitting you could be omitting she could be omitting we could be omitting you could be omitting they could be omitting
Perfect
I could have omitted you could have omitted she 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 she could have been omitting we could have been omitting you could have been omitting they could have been omitting
Negation
Simple form
I couldn't omit you couldn't omit she couldn't omit we couldn't omit you couldn't omit they couldn't omit
V-ing form
I couldn't be omitting you couldn't be omitting she couldn't be omitting we couldn't be omitting you couldn't be omitting they couldn't be omitting
Perfect
I couldn't have omitted you couldn't have omitted she couldn't have omitted we couldn't have omitted you couldn't have omitted they couldn't have omitted
V-ing perfect
I couldn't have been omitting you couldn't have been omitting she couldn't have been omitting we couldn't have been omitting you couldn't have been omitting they couldn't have been omitting
Interrogative form
Simple form
could I omit? could you omit? could she omit? could we omit? could you omit? could they omit?
V-ing form
could I be omitting? could you be omitting? could she be omitting? could we be omitting? could you be omitting? could they be omitting?
Perfect
could I have omitted? could you have omitted? could she 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 she have been omitting? could we have been omitting? could you have been omitting? could they have been omitting?
Interro-negative form
Simple form
couldn't I omit? couldn't you omit? couldn't she omit? couldn't we omit? couldn't you omit? couldn't they omit?
V-ing form
couldn't I be omitting? couldn't you be omitting? couldn't she be omitting? couldn't we be omitting? couldn't you be omitting? couldn't they be omitting?
Perfect
couldn't I have omitted? couldn't you have omitted? couldn't she have omitted? couldn't we have omitted? couldn't you have omitted? couldn't they have omitted?
V-ing perfect
couldn't I have been omitting? couldn't you have been omitting? couldn't she have been omitting? couldn't we have been omitting? couldn't you have been omitting? couldn't they have been omitting?