English verb conjugation
COULD THREAD

Regular verb: thread - threaded - threaded

Affirmation

Simple form	V-ing form
I could thread you could thread she could thread we could thread you could thread they could thread	I could be threading you could be threading she could be threading we could be threading you could be threading they could be threading
Perfect	V-ing perfect
I could have threaded you could have threaded she could have threaded we could have threaded you could have threaded they could have threaded	I could have been threading you could have been threading she could have been threading we could have been threading you could have been threading they could have been threading

Negation

Simple form	V-ing form
I couldn't thread you couldn't thread she couldn't thread we couldn't thread you couldn't thread they couldn't thread	I couldn't be threading you couldn't be threading she couldn't be threading we couldn't be threading you couldn't be threading they couldn't be threading
Perfect	V-ing perfect
I couldn't have threaded you couldn't have threaded she couldn't have threaded we couldn't have threaded you couldn't have threaded they couldn't have threaded	I couldn't have been threading you couldn't have been threading she couldn't have been threading we couldn't have been threading you couldn't have been threading they couldn't have been threading

Interrogative form

Simple form	V-ing form
could I thread? could you thread? could she thread? could we thread? could you thread? could they thread?	could I be threading? could you be threading? could she be threading? could we be threading? could you be threading? could they be threading?
Perfect	V-ing perfect
could I have threaded? could you have threaded? could she have threaded? could we have threaded? could you have threaded? could they have threaded?	could I have been threading? could you have been threading? could she have been threading? could we have been threading? could you have been threading? could they have been threading?

Interro-negative form

Simple form	V-ing form
couldn't I thread? couldn't you thread? couldn't she thread? couldn't we thread? couldn't you thread? couldn't they thread?	couldn't I be threading? couldn't you be threading? couldn't she be threading? couldn't we be threading? couldn't you be threading? couldn't they be threading?
Perfect	V-ing perfect
couldn't I have threaded? couldn't you have threaded? couldn't she have threaded? couldn't we have threaded? couldn't you have threaded? couldn't they have threaded?	couldn't I have been threading? couldn't you have been threading? couldn't she have been threading? couldn't we have been threading? couldn't you have been threading? couldn't they have been threading?