English verb conjugation
COULD STRENGTHEN

Regular verb: strengthen - strengthened - strengthened

Affirmation

Simple form	V-ing form
I could strengthen you could strengthen she could strengthen we could strengthen you could strengthen they could strengthen	I could be strengthening you could be strengthening she could be strengthening we could be strengthening you could be strengthening they could be strengthening
Perfect	V-ing perfect
I could have strengthened you could have strengthened she could have strengthened we could have strengthened you could have strengthened they could have strengthened	I could have been strengthening you could have been strengthening she could have been strengthening we could have been strengthening you could have been strengthening they could have been strengthening

Negation

Simple form	V-ing form
I could not strengthen you could not strengthen she could not strengthen we could not strengthen you could not strengthen they could not strengthen	I could not be strengthening you could not be strengthening she could not be strengthening we could not be strengthening you could not be strengthening they could not be strengthening
Perfect	V-ing perfect
I could not have strengthened you could not have strengthened she could not have strengthened we could not have strengthened you could not have strengthened they could not have strengthened	I could not have been strengthening you could not have been strengthening she could not have been strengthening we could not have been strengthening you could not have been strengthening they could not have been strengthening

Interrogative form

Simple form	V-ing form
could I strengthen? could you strengthen? could she strengthen? could we strengthen? could you strengthen? could they strengthen?	could I be strengthening? could you be strengthening? could she be strengthening? could we be strengthening? could you be strengthening? could they be strengthening?
Perfect	V-ing perfect
could I have strengthened? could you have strengthened? could she have strengthened? could we have strengthened? could you have strengthened? could they have strengthened?	could I have been strengthening? could you have been strengthening? could she have been strengthening? could we have been strengthening? could you have been strengthening? could they have been strengthening?

Interro-negative form

Simple form	V-ing form
could I not strengthen? could you not strengthen? could she not strengthen? could we not strengthen? could you not strengthen? could they not strengthen?	could I not be strengthening? could you not be strengthening? could she not be strengthening? could we not be strengthening? could you not be strengthening? could they not be strengthening?
Perfect	V-ing perfect
could I not have strengthened? could you not have strengthened? could she not have strengthened? could we not have strengthened? could you not have strengthened? could they not have strengthened?	could I not have been strengthening? could you not have been strengthening? could she not have been strengthening? could we not have been strengthening? could you not have been strengthening? could they not have been strengthening?