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