I could weigh you could weigh he could weigh we could weigh you could weigh they could weigh
V-ing form
I could be weighing you could be weighing he could be weighing we could be weighing you could be weighing they could be weighing
Perfect
I could have weighed you could have weighed he could have weighed we could have weighed you could have weighed they could have weighed
V-ing perfect
I could have been weighing you could have been weighing he could have been weighing we could have been weighing you could have been weighing they could have been weighing
Negation
Simple form
I couldn't weigh you couldn't weigh he couldn't weigh we couldn't weigh you couldn't weigh they couldn't weigh
V-ing form
I couldn't be weighing you couldn't be weighing he couldn't be weighing we couldn't be weighing you couldn't be weighing they couldn't be weighing
Perfect
I couldn't have weighed you couldn't have weighed he couldn't have weighed we couldn't have weighed you couldn't have weighed they couldn't have weighed
V-ing perfect
I couldn't have been weighing you couldn't have been weighing he couldn't have been weighing we couldn't have been weighing you couldn't have been weighing they couldn't have been weighing
Interrogative form
Simple form
could I weigh? could you weigh? could he weigh? could we weigh? could you weigh? could they weigh?
V-ing form
could I be weighing? could you be weighing? could he be weighing? could we be weighing? could you be weighing? could they be weighing?
Perfect
could I have weighed? could you have weighed? could he have weighed? could we have weighed? could you have weighed? could they have weighed?
V-ing perfect
could I have been weighing? could you have been weighing? could he have been weighing? could we have been weighing? could you have been weighing? could they have been weighing?
Interro-negative form
Simple form
couldn't I weigh? couldn't you weigh? couldn't he weigh? couldn't we weigh? couldn't you weigh? couldn't they weigh?
V-ing form
couldn't I be weighing? couldn't you be weighing? couldn't he be weighing? couldn't we be weighing? couldn't you be weighing? couldn't they be weighing?
Perfect
couldn't I have weighed? couldn't you have weighed? couldn't he have weighed? couldn't we have weighed? couldn't you have weighed? couldn't they have weighed?
V-ing perfect
couldn't I have been weighing? couldn't you have been weighing? couldn't he have been weighing? couldn't we have been weighing? couldn't you have been weighing? couldn't they have been weighing?