I could stretch you could stretch he could stretch we could stretch you could stretch they could stretch
V-ing form
I could be stretching you could be stretching he could be stretching we could be stretching you could be stretching they could be stretching
Perfect
I could have stretched you could have stretched he 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 he 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 he 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 he 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 he 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 he 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 he stretch? could we stretch? could you stretch? could they stretch?
V-ing form
could I be stretching? could you be stretching? could he be stretching? could we be stretching? could you be stretching? could they be stretching?
Perfect
could I have stretched? could you have stretched? could he 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 he 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 he 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 he 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 he 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 he have been stretching? couldn't we have been stretching? couldn't you have been stretching? couldn't they have been stretching?