I could mix you could mix she could mix we could mix you could mix they could mix
V-ing form
I could be mixing you could be mixing she could be mixing we could be mixing you could be mixing they could be mixing
Perfect
I could have mixed you could have mixed she could have mixed we could have mixed you could have mixed they could have mixed
V-ing perfect
I could have been mixing you could have been mixing she could have been mixing we could have been mixing you could have been mixing they could have been mixing
Negation
Simple form
I could not mix you could not mix she could not mix we could not mix you could not mix they could not mix
V-ing form
I could not be mixing you could not be mixing she could not be mixing we could not be mixing you could not be mixing they could not be mixing
Perfect
I could not have mixed you could not have mixed she could not have mixed we could not have mixed you could not have mixed they could not have mixed
V-ing perfect
I could not have been mixing you could not have been mixing she could not have been mixing we could not have been mixing you could not have been mixing they could not have been mixing
Interrogative form
Simple form
could I mix? could you mix? could she mix? could we mix? could you mix? could they mix?
V-ing form
could I be mixing? could you be mixing? could she be mixing? could we be mixing? could you be mixing? could they be mixing?
Perfect
could I have mixed? could you have mixed? could she have mixed? could we have mixed? could you have mixed? could they have mixed?
V-ing perfect
could I have been mixing? could you have been mixing? could she have been mixing? could we have been mixing? could you have been mixing? could they have been mixing?
Interro-negative form
Simple form
could I not mix? could you not mix? could she not mix? could we not mix? could you not mix? could they not mix?
V-ing form
could I not be mixing? could you not be mixing? could she not be mixing? could we not be mixing? could you not be mixing? could they not be mixing?
Perfect
could I not have mixed? could you not have mixed? could she not have mixed? could we not have mixed? could you not have mixed? could they not have mixed?
V-ing perfect
could I not have been mixing? could you not have been mixing? could she not have been mixing? could we not have been mixing? could you not have been mixing? could they not have been mixing?