I could itch you could itch he could itch we could itch you could itch they could itch
V-ing form
I could be itching you could be itching he could be itching we could be itching you could be itching they could be itching
Perfect
I could have itched you could have itched he could have itched we could have itched you could have itched they could have itched
V-ing perfect
I could have been itching you could have been itching he could have been itching we could have been itching you could have been itching they could have been itching
Negation
Simple form
I could not itch you could not itch he could not itch we could not itch you could not itch they could not itch
V-ing form
I could not be itching you could not be itching he could not be itching we could not be itching you could not be itching they could not be itching
Perfect
I could not have itched you could not have itched he could not have itched we could not have itched you could not have itched they could not have itched
V-ing perfect
I could not have been itching you could not have been itching he could not have been itching we could not have been itching you could not have been itching they could not have been itching
Interrogative form
Simple form
could I itch? could you itch? could he itch? could we itch? could you itch? could they itch?
V-ing form
could I be itching? could you be itching? could he be itching? could we be itching? could you be itching? could they be itching?
Perfect
could I have itched? could you have itched? could he have itched? could we have itched? could you have itched? could they have itched?
V-ing perfect
could I have been itching? could you have been itching? could he have been itching? could we have been itching? could you have been itching? could they have been itching?
Interro-negative form
Simple form
could I not itch? could you not itch? could he not itch? could we not itch? could you not itch? could they not itch?
V-ing form
could I not be itching? could you not be itching? could he not be itching? could we not be itching? could you not be itching? could they not be itching?
Perfect
could I not have itched? could you not have itched? could he not have itched? could we not have itched? could you not have itched? could they not have itched?
V-ing perfect
could I not have been itching? could you not have been itching? could he not have been itching? could we not have been itching? could you not have been itching? could they not have been itching?