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