English verb conjugation
CAN CONTRIBUTE

Regular verb: contribute - contributed - contributed

Affirmation

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

Negation

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

Interrogative form

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

Interro-negative form

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