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