must filter
Verbo regular: filter - filtered- filtered

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must filter
you must filter
he must filter
we must filter
you must filter
they must filter 	I must be filtering
you must be filtering
he must be filtering
we must be filtering
you must be filtering
they must be filtering	I must have filtered
you must have filtered
he must have filtered
we must have filtered
you must have filtered
they must have filtered	I must have been filtering
you must have been filtering
he must have been filtering
we must have been filtering
you must have been filtering
they must have been filtering	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must not filter
you must not filter
he must not filter
we must not filter
you must not filter
they must not filter 	I must not be filtering
you must not be filtering
he must not be filtering
we must not be filtering
you must not be filtering
they must not be filtering	I must not have filtered
you must not have filtered
he must not have filtered
we must not have filtered
you must not have filtered
they must not have filtered	I must not have been filtering
you must not have been filtering
he must not have been filtering
we must not have been filtering
you must not have been filtering
they must not have been filtering	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I filter?
must you filter?
must he filter?
must we filter?
must you filter?
must they filter? 	must I be filtering?
must you be filtering?
must he be filtering?
must we be filtering?
must you be filtering?
must they be filtering? 	must I have filtered?
must you have filtered?
must he have filtered?
must we have filtered?
must you have filtered?
must they have filtered? 	must I have been filtering?
must you have been filtering?
must he have been filtering?
must we have been filtering?
must you have been filtering?
must they have been filtering? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I not filter?
must you not filter?
must he not filter?
must we not filter?
must you not filter?
must they not filter? 	must I not be filtering?
must you not be filtering?
must he not be filtering?
must we not be filtering?
must you not be filtering?
must they not be filtering? 	must I not have filtered?
must you not have filtered?
must he not have filtered?
must we not have filtered?
must you not have filtered?
must they not have filtered? 	must I not have been filtering?
must you not have been filtering?
must he not have been filtering?
must we not have been filtering?
must you not have been filtering?
must they not have been filtering?