English verb conjugation
COULD SHARPEN

Regular verb: sharpen - sharpened - sharpened

Affirmation

Simple form	V-ing form
I could sharpen you could sharpen she could sharpen we could sharpen you could sharpen they could sharpen	I could be sharpening you could be sharpening she could be sharpening we could be sharpening you could be sharpening they could be sharpening
Perfect	V-ing perfect
I could have sharpened you could have sharpened she could have sharpened we could have sharpened you could have sharpened they could have sharpened	I could have been sharpening you could have been sharpening she could have been sharpening we could have been sharpening you could have been sharpening they could have been sharpening

Negation

Simple form	V-ing form
I couldn't sharpen you couldn't sharpen she couldn't sharpen we couldn't sharpen you couldn't sharpen they couldn't sharpen	I couldn't be sharpening you couldn't be sharpening she couldn't be sharpening we couldn't be sharpening you couldn't be sharpening they couldn't be sharpening
Perfect	V-ing perfect
I couldn't have sharpened you couldn't have sharpened she couldn't have sharpened we couldn't have sharpened you couldn't have sharpened they couldn't have sharpened	I couldn't have been sharpening you couldn't have been sharpening she couldn't have been sharpening we couldn't have been sharpening you couldn't have been sharpening they couldn't have been sharpening

Interrogative form

Simple form	V-ing form
could I sharpen? could you sharpen? could she sharpen? could we sharpen? could you sharpen? could they sharpen?	could I be sharpening? could you be sharpening? could she be sharpening? could we be sharpening? could you be sharpening? could they be sharpening?
Perfect	V-ing perfect
could I have sharpened? could you have sharpened? could she have sharpened? could we have sharpened? could you have sharpened? could they have sharpened?	could I have been sharpening? could you have been sharpening? could she have been sharpening? could we have been sharpening? could you have been sharpening? could they have been sharpening?

Interro-negative form

Simple form	V-ing form
couldn't I sharpen? couldn't you sharpen? couldn't she sharpen? couldn't we sharpen? couldn't you sharpen? couldn't they sharpen?	couldn't I be sharpening? couldn't you be sharpening? couldn't she be sharpening? couldn't we be sharpening? couldn't you be sharpening? couldn't they be sharpening?
Perfect	V-ing perfect
couldn't I have sharpened? couldn't you have sharpened? couldn't she have sharpened? couldn't we have sharpened? couldn't you have sharpened? couldn't they have sharpened?	couldn't I have been sharpening? couldn't you have been sharpening? couldn't she have been sharpening? couldn't we have been sharpening? couldn't you have been sharpening? couldn't they have been sharpening?