English verb conjugation
COULD FASTEN

Regular verb: fasten - fastened - fastened

Affirmation

Simple form	V-ing form
I could fasten you could fasten she could fasten we could fasten you could fasten they could fasten	I could be fastening you could be fastening she 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 she 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 she 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 couldn't fasten you couldn't fasten she couldn't fasten we couldn't fasten you couldn't fasten they couldn't fasten	I couldn't be fastening you couldn't be fastening she couldn't be fastening we couldn't be fastening you couldn't be fastening they couldn't be fastening
Perfect	V-ing perfect
I couldn't have fastened you couldn't have fastened she couldn't have fastened we couldn't have fastened you couldn't have fastened they couldn't have fastened	I couldn't have been fastening you couldn't have been fastening she couldn't have been fastening we couldn't have been fastening you couldn't have been fastening they couldn't have been fastening

Interrogative form

Simple form	V-ing form
could I fasten? could you fasten? could she fasten? could we fasten? could you fasten? could they fasten?	could I be fastening? could you be fastening? could she 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 she 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 she 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
couldn't I fasten? couldn't you fasten? couldn't she fasten? couldn't we fasten? couldn't you fasten? couldn't they fasten?	couldn't I be fastening? couldn't you be fastening? couldn't she be fastening? couldn't we be fastening? couldn't you be fastening? couldn't they be fastening?
Perfect	V-ing perfect
couldn't I have fastened? couldn't you have fastened? couldn't she have fastened? couldn't we have fastened? couldn't you have fastened? couldn't they have fastened?	couldn't I have been fastening? couldn't you have been fastening? couldn't she have been fastening? couldn't we have been fastening? couldn't you have been fastening? couldn't they have been fastening?