must impair
Regular verb: impair - impaired- impaired

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must impair
you must impair
he must impair
we must impair
you must impair
they must impair 	I must be impairing
you must be impairing
he must be impairing
we must be impairing
you must be impairing
they must be impairing	I must have impaired
you must have impaired
he must have impaired
we must have impaired
you must have impaired
they must have impaired	I must have been impairing
you must have been impairing
he must have been impairing
we must have been impairing
you must have been impairing
they must have been impairing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must not impair
you must not impair
he must not impair
we must not impair
you must not impair
they must not impair 	I must not be impairing
you must not be impairing
he must not be impairing
we must not be impairing
you must not be impairing
they must not be impairing	I must not have impaired
you must not have impaired
he must not have impaired
we must not have impaired
you must not have impaired
they must not have impaired	I must not have been impairing
you must not have been impairing
he must not have been impairing
we must not have been impairing
you must not have been impairing
they must not have been impairing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I impair?
must you impair?
must he impair?
must we impair?
must you impair?
must they impair? 	must I be impairing?
must you be impairing?
must he be impairing?
must we be impairing?
must you be impairing?
must they be impairing? 	must I have impaired?
must you have impaired?
must he have impaired?
must we have impaired?
must you have impaired?
must they have impaired? 	must I have been impairing?
must you have been impairing?
must he have been impairing?
must we have been impairing?
must you have been impairing?
must they have been impairing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I not impair?
must you not impair?
must he not impair?
must we not impair?
must you not impair?
must they not impair? 	must I not be impairing?
must you not be impairing?
must he not be impairing?
must we not be impairing?
must you not be impairing?
must they not be impairing? 	must I not have impaired?
must you not have impaired?
must he not have impaired?
must we not have impaired?
must you not have impaired?
must they not have impaired? 	must I not have been impairing?
must you not have been impairing?
must he not have been impairing?
must we not have been impairing?
must you not have been impairing?
must they not have been impairing?