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