English verb conjugation
COULD FASTEN

Regular verb: fasten - fastened - fastened

Affirmation

Simple form	V-ing form
I could fasten you could fasten he could fasten we could fasten you could fasten they could fasten	I could be fastening you could be fastening he could be fastening we could be fastening you could be fastening they could be fastening
Perfect	V-ing perfect
I could have fastened you could have fastened he could have fastened we could have fastened you could have fastened they could have fastened	I could have been fastening you could have been fastening he could have been fastening we could have been fastening you could have been fastening they could have been fastening

Negation

Simple form	V-ing form
I could not fasten you could not fasten he could not fasten we could not fasten you could not fasten they could not fasten	I could not be fastening you could not be fastening he could not be fastening we could not be fastening you could not be fastening they could not be fastening
Perfect	V-ing perfect
I could not have fastened you could not have fastened he could not have fastened we could not have fastened you could not have fastened they could not have fastened	I could not have been fastening you could not have been fastening he could not have been fastening we could not have been fastening you could not have been fastening they could not have been fastening

Interrogative form

Simple form	V-ing form
could I fasten? could you fasten? could he fasten? could we fasten? could you fasten? could they fasten?	could I be fastening? could you be fastening? could he be fastening? could we be fastening? could you be fastening? could they be fastening?
Perfect	V-ing perfect
could I have fastened? could you have fastened? could he have fastened? could we have fastened? could you have fastened? could they have fastened?	could I have been fastening? could you have been fastening? could he have been fastening? could we have been fastening? could you have been fastening? could they have been fastening?

Interro-negative form

Simple form	V-ing form
could I not fasten? could you not fasten? could he not fasten? could we not fasten? could you not fasten? could they not fasten?	could I not be fastening? could you not be fastening? could he not be fastening? could we not be fastening? could you not be fastening? could they not be fastening?
Perfect	V-ing perfect
could I not have fastened? could you not have fastened? could he not have fastened? could we not have fastened? could you not have fastened? could they not have fastened?	could I not have been fastening? could you not have been fastening? could he not have been fastening? could we not have been fastening? could you not have been fastening? could they not have been fastening?