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