English verb conjugation
COULD CONTRIBUTE

Regular verb: contribute - contributed - contributed

Affirmation

Simple form	V-ing form
I could contribute you could contribute he could contribute we could contribute you could contribute they could contribute	I could be contributing you could be contributing he could be contributing we could be contributing you could be contributing they could be contributing
Perfect	V-ing perfect
I could have contributed you could have contributed he could have contributed we could have contributed you could have contributed they could have contributed	I could have been contributing you could have been contributing he could have been contributing we could have been contributing you could have been contributing they could have been contributing

Negation

Simple form	V-ing form
I could not contribute you could not contribute he could not contribute we could not contribute you could not contribute they could not contribute	I could not be contributing you could not be contributing he could not be contributing we could not be contributing you could not be contributing they could not be contributing
Perfect	V-ing perfect
I could not have contributed you could not have contributed he could not have contributed we could not have contributed you could not have contributed they could not have contributed	I could not have been contributing you could not have been contributing he could not have been contributing we could not have been contributing you could not have been contributing they could not have been contributing

Interrogative form

Simple form	V-ing form
could I contribute? could you contribute? could he contribute? could we contribute? could you contribute? could they contribute?	could I be contributing? could you be contributing? could he be contributing? could we be contributing? could you be contributing? could they be contributing?
Perfect	V-ing perfect
could I have contributed? could you have contributed? could he have contributed? could we have contributed? could you have contributed? could they have contributed?	could I have been contributing? could you have been contributing? could he have been contributing? could we have been contributing? could you have been contributing? could they have been contributing?

Interro-negative form

Simple form	V-ing form
could I not contribute? could you not contribute? could he not contribute? could we not contribute? could you not contribute? could they not contribute?	could I not be contributing? could you not be contributing? could he not be contributing? could we not be contributing? could you not be contributing? could they not be contributing?
Perfect	V-ing perfect
could I not have contributed? could you not have contributed? could he not have contributed? could we not have contributed? could you not have contributed? could they not have contributed?	could I not have been contributing? could you not have been contributing? could he not have been contributing? could we not have been contributing? could you not have been contributing? could they not have been contributing?