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