could research
Regular verb: research - researched- researched

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could research
you could research
she could research
we could research
you could research
they could research 	I could be researching
you could be researching
she could be researching
we could be researching
you could be researching
they could be researching	I could have researched
you could have researched
she could have researched
we could have researched
you could have researched
they could have researched	I could have been researching
you could have been researching
she could have been researching
we could have been researching
you could have been researching
they could have been researching	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not research
you could not research
she could not research
we could not research
you could not research
they could not research 	I could not be researching
you could not be researching
she could not be researching
we could not be researching
you could not be researching
they could not be researching	I could not have researched
you could not have researched
she could not have researched
we could not have researched
you could not have researched
they could not have researched	I could not have been researching
you could not have been researching
she could not have been researching
we could not have been researching
you could not have been researching
they could not have been researching	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I research?
could you research?
could she research?
could we research?
could you research?
could they research? 	could I be researching?
could you be researching?
could she be researching?
could we be researching?
could you be researching?
could they be researching? 	could I have researched?
could you have researched?
could she have researched?
could we have researched?
could you have researched?
could they have researched? 	could I have been researching?
could you have been researching?
could she have been researching?
could we have been researching?
could you have been researching?
could they have been researching? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not research?
could you not research?
could she not research?
could we not research?
could you not research?
could they not research? 	could I not be researching?
could you not be researching?
could she not be researching?
could we not be researching?
could you not be researching?
could they not be researching? 	could I not have researched?
could you not have researched?
could she not have researched?
could we not have researched?
could you not have researched?
could they not have researched? 	could I not have been researching?
could you not have been researching?
could she not have been researching?
could we not have been researching?
could you not have been researching?
could they not have been researching?