could stumble
Regular verb: stumble - stumbled- stumbled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could stumble
you could stumble
she could stumble
we could stumble
you could stumble
they could stumble 	I could be stumbling
you could be stumbling
she could be stumbling
we could be stumbling
you could be stumbling
they could be stumbling	I could have stumbled
you could have stumbled
she could have stumbled
we could have stumbled
you could have stumbled
they could have stumbled	I could have been stumbling
you could have been stumbling
she could have been stumbling
we could have been stumbling
you could have been stumbling
they could have been stumbling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not stumble
you could not stumble
she could not stumble
we could not stumble
you could not stumble
they could not stumble 	I could not be stumbling
you could not be stumbling
she could not be stumbling
we could not be stumbling
you could not be stumbling
they could not be stumbling	I could not have stumbled
you could not have stumbled
she could not have stumbled
we could not have stumbled
you could not have stumbled
they could not have stumbled	I could not have been stumbling
you could not have been stumbling
she could not have been stumbling
we could not have been stumbling
you could not have been stumbling
they could not have been stumbling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I stumble?
could you stumble?
could she stumble?
could we stumble?
could you stumble?
could they stumble? 	could I be stumbling?
could you be stumbling?
could she be stumbling?
could we be stumbling?
could you be stumbling?
could they be stumbling? 	could I have stumbled?
could you have stumbled?
could she have stumbled?
could we have stumbled?
could you have stumbled?
could they have stumbled? 	could I have been stumbling?
could you have been stumbling?
could she have been stumbling?
could we have been stumbling?
could you have been stumbling?
could they have been stumbling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not stumble?
could you not stumble?
could she not stumble?
could we not stumble?
could you not stumble?
could they not stumble? 	could I not be stumbling?
could you not be stumbling?
could she not be stumbling?
could we not be stumbling?
could you not be stumbling?
could they not be stumbling? 	could I not have stumbled?
could you not have stumbled?
could she not have stumbled?
could we not have stumbled?
could you not have stumbled?
could they not have stumbled? 	could I not have been stumbling?
could you not have been stumbling?
could she not have been stumbling?
could we not have been stumbling?
could you not have been stumbling?
could they not have been stumbling?