I could garden you could garden he could garden we could garden you could garden they could garden
V-ing form
I could be gardening you could be gardening he could be gardening we could be gardening you could be gardening they could be gardening
Perfect
I could have gardened you could have gardened he could have gardened we could have gardened you could have gardened they could have gardened
V-ing perfect
I could have been gardening you could have been gardening he could have been gardening we could have been gardening you could have been gardening they could have been gardening
Negation
Simple form
I could not garden you could not garden he could not garden we could not garden you could not garden they could not garden
V-ing form
I could not be gardening you could not be gardening he could not be gardening we could not be gardening you could not be gardening they could not be gardening
Perfect
I could not have gardened you could not have gardened he could not have gardened we could not have gardened you could not have gardened they could not have gardened
V-ing perfect
I could not have been gardening you could not have been gardening he could not have been gardening we could not have been gardening you could not have been gardening they could not have been gardening
Interrogative form
Simple form
could I garden? could you garden? could he garden? could we garden? could you garden? could they garden?
V-ing form
could I be gardening? could you be gardening? could he be gardening? could we be gardening? could you be gardening? could they be gardening?
Perfect
could I have gardened? could you have gardened? could he have gardened? could we have gardened? could you have gardened? could they have gardened?
V-ing perfect
could I have been gardening? could you have been gardening? could he have been gardening? could we have been gardening? could you have been gardening? could they have been gardening?
Interro-negative form
Simple form
could I not garden? could you not garden? could he not garden? could we not garden? could you not garden? could they not garden?
V-ing form
could I not be gardening? could you not be gardening? could he not be gardening? could we not be gardening? could you not be gardening? could they not be gardening?
Perfect
could I not have gardened? could you not have gardened? could he not have gardened? could we not have gardened? could you not have gardened? could they not have gardened?
V-ing perfect
could I not have been gardening? could you not have been gardening? could he not have been gardening? could we not have been gardening? could you not have been gardening? could they not have been gardening?