must mask
Verbo regular: mask - masked- masked

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must mask
you must mask
he must mask
we must mask
you must mask
they must mask 	I must be masking
you must be masking
he must be masking
we must be masking
you must be masking
they must be masking	I must have masked
you must have masked
he must have masked
we must have masked
you must have masked
they must have masked	I must have been masking
you must have been masking
he must have been masking
we must have been masking
you must have been masking
they must have been masking	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must not mask
you must not mask
he must not mask
we must not mask
you must not mask
they must not mask 	I must not be masking
you must not be masking
he must not be masking
we must not be masking
you must not be masking
they must not be masking	I must not have masked
you must not have masked
he must not have masked
we must not have masked
you must not have masked
they must not have masked	I must not have been masking
you must not have been masking
he must not have been masking
we must not have been masking
you must not have been masking
they must not have been masking	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I mask?
must you mask?
must he mask?
must we mask?
must you mask?
must they mask? 	must I be masking?
must you be masking?
must he be masking?
must we be masking?
must you be masking?
must they be masking? 	must I have masked?
must you have masked?
must he have masked?
must we have masked?
must you have masked?
must they have masked? 	must I have been masking?
must you have been masking?
must he have been masking?
must we have been masking?
must you have been masking?
must they have been masking? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I not mask?
must you not mask?
must he not mask?
must we not mask?
must you not mask?
must they not mask? 	must I not be masking?
must you not be masking?
must he not be masking?
must we not be masking?
must you not be masking?
must they not be masking? 	must I not have masked?
must you not have masked?
must he not have masked?
must we not have masked?
must you not have masked?
must they not have masked? 	must I not have been masking?
must you not have been masking?
must he not have been masking?
must we not have been masking?
must you not have been masking?
must they not have been masking?