I could stagnate you could stagnate she could stagnate we could stagnate you could stagnate they could stagnate
V-ing form
I could be stagnating you could be stagnating she could be stagnating we could be stagnating you could be stagnating they could be stagnating
Perfect
I could have stagnated you could have stagnated she could have stagnated we could have stagnated you could have stagnated they could have stagnated
V-ing perfect
I could have been stagnating you could have been stagnating she could have been stagnating we could have been stagnating you could have been stagnating they could have been stagnating
Negation
Simple form
I could not stagnate you could not stagnate she could not stagnate we could not stagnate you could not stagnate they could not stagnate
V-ing form
I could not be stagnating you could not be stagnating she could not be stagnating we could not be stagnating you could not be stagnating they could not be stagnating
Perfect
I could not have stagnated you could not have stagnated she could not have stagnated we could not have stagnated you could not have stagnated they could not have stagnated
V-ing perfect
I could not have been stagnating you could not have been stagnating she could not have been stagnating we could not have been stagnating you could not have been stagnating they could not have been stagnating
Interrogative form
Simple form
could I stagnate? could you stagnate? could she stagnate? could we stagnate? could you stagnate? could they stagnate?
V-ing form
could I be stagnating? could you be stagnating? could she be stagnating? could we be stagnating? could you be stagnating? could they be stagnating?
Perfect
could I have stagnated? could you have stagnated? could she have stagnated? could we have stagnated? could you have stagnated? could they have stagnated?
V-ing perfect
could I have been stagnating? could you have been stagnating? could she have been stagnating? could we have been stagnating? could you have been stagnating? could they have been stagnating?
Interro-negative form
Simple form
could I not stagnate? could you not stagnate? could she not stagnate? could we not stagnate? could you not stagnate? could they not stagnate?
V-ing form
could I not be stagnating? could you not be stagnating? could she not be stagnating? could we not be stagnating? could you not be stagnating? could they not be stagnating?
Perfect
could I not have stagnated? could you not have stagnated? could she not have stagnated? could we not have stagnated? could you not have stagnated? could they not have stagnated?
V-ing perfect
could I not have been stagnating? could you not have been stagnating? could she not have been stagnating? could we not have been stagnating? could you not have been stagnating? could they not have been stagnating?