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