could contribute
Verbo regular: contribute - contributed- contributed

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
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	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I couldn't contribute
you couldn't contribute
she couldn't contribute
we couldn't contribute
you couldn't contribute
they couldn't contribute 	I couldn't be contributing
you couldn't be contributing
she couldn't be contributing
we couldn't be contributing
you couldn't be contributing
they couldn't be contributing	I couldn't have contributed
you couldn't have contributed
she couldn't have contributed
we couldn't have contributed
you couldn't have contributed
they couldn't have contributed	I couldn't have been contributing
you couldn't have been contributing
she couldn't have been contributing
we couldn't have been contributing
you couldn't have been contributing
they couldn't have been contributing	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
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? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
couldn't I contribute?
couldn't you contribute?
couldn't she contribute?
couldn't we contribute?
couldn't you contribute?
couldn't they contribute? 	couldn't I be contributing?
couldn't you be contributing?
couldn't she be contributing?
couldn't we be contributing?
couldn't you be contributing?
couldn't they be contributing? 	couldn't I have contributed?
couldn't you have contributed?
couldn't she have contributed?
couldn't we have contributed?
couldn't you have contributed?
couldn't they have contributed? 	couldn't I have been contributing?
couldn't you have been contributing?
couldn't she have been contributing?
couldn't we have been contributing?
couldn't you have been contributing?
couldn't they have been contributing?