I could stretch you could stretch she could stretch we could stretch you could stretch they could stretch
V-ing form
I could be stretching you could be stretching she could be stretching we could be stretching you could be stretching they could be stretching
Perfect
I could have stretched you could have stretched she could have stretched we could have stretched you could have stretched they could have stretched
V-ing perfect
I could have been stretching you could have been stretching she could have been stretching we could have been stretching you could have been stretching they could have been stretching
Negation
Simple form
I couldn't stretch you couldn't stretch she couldn't stretch we couldn't stretch you couldn't stretch they couldn't stretch
V-ing form
I couldn't be stretching you couldn't be stretching she couldn't be stretching we couldn't be stretching you couldn't be stretching they couldn't be stretching
Perfect
I couldn't have stretched you couldn't have stretched she couldn't have stretched we couldn't have stretched you couldn't have stretched they couldn't have stretched
V-ing perfect
I couldn't have been stretching you couldn't have been stretching she couldn't have been stretching we couldn't have been stretching you couldn't have been stretching they couldn't have been stretching
Interrogative form
Simple form
could I stretch? could you stretch? could she stretch? could we stretch? could you stretch? could they stretch?
V-ing form
could I be stretching? could you be stretching? could she be stretching? could we be stretching? could you be stretching? could they be stretching?
Perfect
could I have stretched? could you have stretched? could she have stretched? could we have stretched? could you have stretched? could they have stretched?
V-ing perfect
could I have been stretching? could you have been stretching? could she have been stretching? could we have been stretching? could you have been stretching? could they have been stretching?
Interro-negative form
Simple form
couldn't I stretch? couldn't you stretch? couldn't she stretch? couldn't we stretch? couldn't you stretch? couldn't they stretch?
V-ing form
couldn't I be stretching? couldn't you be stretching? couldn't she be stretching? couldn't we be stretching? couldn't you be stretching? couldn't they be stretching?
Perfect
couldn't I have stretched? couldn't you have stretched? couldn't she have stretched? couldn't we have stretched? couldn't you have stretched? couldn't they have stretched?
V-ing perfect
couldn't I have been stretching? couldn't you have been stretching? couldn't she have been stretching? couldn't we have been stretching? couldn't you have been stretching? couldn't they have been stretching?