I could experiment you could experiment she could experiment we could experiment you could experiment they could experiment
V-ing form
I could be experimenting you could be experimenting she could be experimenting we could be experimenting you could be experimenting they could be experimenting
Perfect
I could have experimented you could have experimented she could have experimented we could have experimented you could have experimented they could have experimented
V-ing perfect
I could have been experimenting you could have been experimenting she could have been experimenting we could have been experimenting you could have been experimenting they could have been experimenting
Negation
Simple form
I could not experiment you could not experiment she could not experiment we could not experiment you could not experiment they could not experiment
V-ing form
I could not be experimenting you could not be experimenting she could not be experimenting we could not be experimenting you could not be experimenting they could not be experimenting
Perfect
I could not have experimented you could not have experimented she could not have experimented we could not have experimented you could not have experimented they could not have experimented
V-ing perfect
I could not have been experimenting you could not have been experimenting she could not have been experimenting we could not have been experimenting you could not have been experimenting they could not have been experimenting
Interrogative form
Simple form
could I experiment? could you experiment? could she experiment? could we experiment? could you experiment? could they experiment?
V-ing form
could I be experimenting? could you be experimenting? could she be experimenting? could we be experimenting? could you be experimenting? could they be experimenting?
Perfect
could I have experimented? could you have experimented? could she have experimented? could we have experimented? could you have experimented? could they have experimented?
V-ing perfect
could I have been experimenting? could you have been experimenting? could she have been experimenting? could we have been experimenting? could you have been experimenting? could they have been experimenting?
Interro-negative form
Simple form
could I not experiment? could you not experiment? could she not experiment? could we not experiment? could you not experiment? could they not experiment?
V-ing form
could I not be experimenting? could you not be experimenting? could she not be experimenting? could we not be experimenting? could you not be experimenting? could they not be experimenting?
Perfect
could I not have experimented? could you not have experimented? could she not have experimented? could we not have experimented? could you not have experimented? could they not have experimented?
V-ing perfect
could I not have been experimenting? could you not have been experimenting? could she not have been experimenting? could we not have been experimenting? could you not have been experimenting? could they not have been experimenting?