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