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 couldn't itch you couldn't itch he couldn't itch we couldn't itch you couldn't itch they couldn't itch
V-ing form
I couldn't be itching you couldn't be itching he couldn't be itching we couldn't be itching you couldn't be itching they couldn't be itching
Perfect
I couldn't have itched you couldn't have itched he couldn't have itched we couldn't have itched you couldn't have itched they couldn't have itched
V-ing perfect
I couldn't have been itching you couldn't have been itching he couldn't have been itching we couldn't have been itching you couldn't have been itching they couldn't 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
couldn't I itch? couldn't you itch? couldn't he itch? couldn't we itch? couldn't you itch? couldn't they itch?
V-ing form
couldn't I be itching? couldn't you be itching? couldn't he be itching? couldn't we be itching? couldn't you be itching? couldn't they be itching?
Perfect
couldn't I have itched? couldn't you have itched? couldn't he have itched? couldn't we have itched? couldn't you have itched? couldn't they have itched?
V-ing perfect
couldn't I have been itching? couldn't you have been itching? couldn't he have been itching? couldn't we have been itching? couldn't you have been itching? couldn't they have been itching?