English verb conjugation
COULD CURVE

Regular verb: curve - curved - curved

Affirmation

Simple form	V-ing form
I could curve you could curve he could curve we could curve you could curve they could curve	I could be curving you could be curving he could be curving we could be curving you could be curving they could be curving
Perfect	V-ing perfect
I could have curved you could have curved he could have curved we could have curved you could have curved they could have curved	I could have been curving you could have been curving he could have been curving we could have been curving you could have been curving they could have been curving

Negation

Simple form	V-ing form
I couldn't curve you couldn't curve he couldn't curve we couldn't curve you couldn't curve they couldn't curve	I couldn't be curving you couldn't be curving he couldn't be curving we couldn't be curving you couldn't be curving they couldn't be curving
Perfect	V-ing perfect
I couldn't have curved you couldn't have curved he couldn't have curved we couldn't have curved you couldn't have curved they couldn't have curved	I couldn't have been curving you couldn't have been curving he couldn't have been curving we couldn't have been curving you couldn't have been curving they couldn't have been curving

Interrogative form

Simple form	V-ing form
could I curve? could you curve? could he curve? could we curve? could you curve? could they curve?	could I be curving? could you be curving? could he be curving? could we be curving? could you be curving? could they be curving?
Perfect	V-ing perfect
could I have curved? could you have curved? could he have curved? could we have curved? could you have curved? could they have curved?	could I have been curving? could you have been curving? could he have been curving? could we have been curving? could you have been curving? could they have been curving?

Interro-negative form

Simple form	V-ing form
couldn't I curve? couldn't you curve? couldn't he curve? couldn't we curve? couldn't you curve? couldn't they curve?	couldn't I be curving? couldn't you be curving? couldn't he be curving? couldn't we be curving? couldn't you be curving? couldn't they be curving?
Perfect	V-ing perfect
couldn't I have curved? couldn't you have curved? couldn't he have curved? couldn't we have curved? couldn't you have curved? couldn't they have curved?	couldn't I have been curving? couldn't you have been curving? couldn't he have been curving? couldn't we have been curving? couldn't you have been curving? couldn't they have been curving?