I could choir you could choir he could choir we could choir you could choir they could choir
V-ing form
I could be choiring you could be choiring he could be choiring we could be choiring you could be choiring they could be choiring
Perfect
I could have choired you could have choired he could have choired we could have choired you could have choired they could have choired
V-ing perfect
I could have been choiring you could have been choiring he could have been choiring we could have been choiring you could have been choiring they could have been choiring
Negation
Simple form
I couldn't choir you couldn't choir he couldn't choir we couldn't choir you couldn't choir they couldn't choir
V-ing form
I couldn't be choiring you couldn't be choiring he couldn't be choiring we couldn't be choiring you couldn't be choiring they couldn't be choiring
Perfect
I couldn't have choired you couldn't have choired he couldn't have choired we couldn't have choired you couldn't have choired they couldn't have choired
V-ing perfect
I couldn't have been choiring you couldn't have been choiring he couldn't have been choiring we couldn't have been choiring you couldn't have been choiring they couldn't have been choiring
Interrogative form
Simple form
could I choir? could you choir? could he choir? could we choir? could you choir? could they choir?
V-ing form
could I be choiring? could you be choiring? could he be choiring? could we be choiring? could you be choiring? could they be choiring?
Perfect
could I have choired? could you have choired? could he have choired? could we have choired? could you have choired? could they have choired?
V-ing perfect
could I have been choiring? could you have been choiring? could he have been choiring? could we have been choiring? could you have been choiring? could they have been choiring?
Interro-negative form
Simple form
couldn't I choir? couldn't you choir? couldn't he choir? couldn't we choir? couldn't you choir? couldn't they choir?
V-ing form
couldn't I be choiring? couldn't you be choiring? couldn't he be choiring? couldn't we be choiring? couldn't you be choiring? couldn't they be choiring?
Perfect
couldn't I have choired? couldn't you have choired? couldn't he have choired? couldn't we have choired? couldn't you have choired? couldn't they have choired?
V-ing perfect
couldn't I have been choiring? couldn't you have been choiring? couldn't he have been choiring? couldn't we have been choiring? couldn't you have been choiring? couldn't they have been choiring?