I could buckle you could buckle she could buckle we could buckle you could buckle they could buckle
V-ing form
I could be buckling you could be buckling she could be buckling we could be buckling you could be buckling they could be buckling
Perfect
I could have buckled you could have buckled she could have buckled we could have buckled you could have buckled they could have buckled
V-ing perfect
I could have been buckling you could have been buckling she could have been buckling we could have been buckling you could have been buckling they could have been buckling
Negation
Simple form
I could not buckle you could not buckle she could not buckle we could not buckle you could not buckle they could not buckle
V-ing form
I could not be buckling you could not be buckling she could not be buckling we could not be buckling you could not be buckling they could not be buckling
Perfect
I could not have buckled you could not have buckled she could not have buckled we could not have buckled you could not have buckled they could not have buckled
V-ing perfect
I could not have been buckling you could not have been buckling she could not have been buckling we could not have been buckling you could not have been buckling they could not have been buckling
Interrogative form
Simple form
could I buckle? could you buckle? could she buckle? could we buckle? could you buckle? could they buckle?
V-ing form
could I be buckling? could you be buckling? could she be buckling? could we be buckling? could you be buckling? could they be buckling?
Perfect
could I have buckled? could you have buckled? could she have buckled? could we have buckled? could you have buckled? could they have buckled?
V-ing perfect
could I have been buckling? could you have been buckling? could she have been buckling? could we have been buckling? could you have been buckling? could they have been buckling?
Interro-negative form
Simple form
could I not buckle? could you not buckle? could she not buckle? could we not buckle? could you not buckle? could they not buckle?
V-ing form
could I not be buckling? could you not be buckling? could she not be buckling? could we not be buckling? could you not be buckling? could they not be buckling?
Perfect
could I not have buckled? could you not have buckled? could she not have buckled? could we not have buckled? could you not have buckled? could they not have buckled?
V-ing perfect
could I not have been buckling? could you not have been buckling? could she not have been buckling? could we not have been buckling? could you not have been buckling? could they not have been buckling?