could contribute
Regular verb: contribute - contributed- contributed

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