must double
Regular verb: double - doubled- doubled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must double
you must double
she must double
we must double
you must double
they must double 	I must be doubling
you must be doubling
she must be doubling
we must be doubling
you must be doubling
they must be doubling	I must have doubled
you must have doubled
she must have doubled
we must have doubled
you must have doubled
they must have doubled	I must have been doubling
you must have been doubling
she must have been doubling
we must have been doubling
you must have been doubling
they must have been doubling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must not double
you must not double
she must not double
we must not double
you must not double
they must not double 	I must not be doubling
you must not be doubling
she must not be doubling
we must not be doubling
you must not be doubling
they must not be doubling	I must not have doubled
you must not have doubled
she must not have doubled
we must not have doubled
you must not have doubled
they must not have doubled	I must not have been doubling
you must not have been doubling
she must not have been doubling
we must not have been doubling
you must not have been doubling
they must not have been doubling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I double?
must you double?
must she double?
must we double?
must you double?
must they double? 	must I be doubling?
must you be doubling?
must she be doubling?
must we be doubling?
must you be doubling?
must they be doubling? 	must I have doubled?
must you have doubled?
must she have doubled?
must we have doubled?
must you have doubled?
must they have doubled? 	must I have been doubling?
must you have been doubling?
must she have been doubling?
must we have been doubling?
must you have been doubling?
must they have been doubling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I not double?
must you not double?
must she not double?
must we not double?
must you not double?
must they not double? 	must I not be doubling?
must you not be doubling?
must she not be doubling?
must we not be doubling?
must you not be doubling?
must they not be doubling? 	must I not have doubled?
must you not have doubled?
must she not have doubled?
must we not have doubled?
must you not have doubled?
must they not have doubled? 	must I not have been doubling?
must you not have been doubling?
must she not have been doubling?
must we not have been doubling?
must you not have been doubling?
must they not have been doubling?