must sustain
Verbo regular: sustain - sustained- sustained

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must sustain
you must sustain
she must sustain
we must sustain
you must sustain
they must sustain 	I must be sustaining
you must be sustaining
she must be sustaining
we must be sustaining
you must be sustaining
they must be sustaining	I must have sustained
you must have sustained
she must have sustained
we must have sustained
you must have sustained
they must have sustained	I must have been sustaining
you must have been sustaining
she must have been sustaining
we must have been sustaining
you must have been sustaining
they must have been sustaining	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I mustn't sustain
you mustn't sustain
she mustn't sustain
we mustn't sustain
you mustn't sustain
they mustn't sustain 	I mustn't be sustaining
you mustn't be sustaining
she mustn't be sustaining
we mustn't be sustaining
you mustn't be sustaining
they mustn't be sustaining	I mustn't have sustained
you mustn't have sustained
she mustn't have sustained
we mustn't have sustained
you mustn't have sustained
they mustn't have sustained	I mustn't have been sustaining
you mustn't have been sustaining
she mustn't have been sustaining
we mustn't have been sustaining
you mustn't have been sustaining
they mustn't have been sustaining	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I sustain?
must you sustain?
must she sustain?
must we sustain?
must you sustain?
must they sustain? 	must I be sustaining?
must you be sustaining?
must she be sustaining?
must we be sustaining?
must you be sustaining?
must they be sustaining? 	must I have sustained?
must you have sustained?
must she have sustained?
must we have sustained?
must you have sustained?
must they have sustained? 	must I have been sustaining?
must you have been sustaining?
must she have been sustaining?
must we have been sustaining?
must you have been sustaining?
must they have been sustaining? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
mustn't I sustain?
mustn't you sustain?
mustn't she sustain?
mustn't we sustain?
mustn't you sustain?
mustn't they sustain? 	mustn't I be sustaining?
mustn't you be sustaining?
mustn't she be sustaining?
mustn't we be sustaining?
mustn't you be sustaining?
mustn't they be sustaining? 	mustn't I have sustained?
mustn't you have sustained?
mustn't she have sustained?
mustn't we have sustained?
mustn't you have sustained?
mustn't they have sustained? 	mustn't I have been sustaining?
mustn't you have been sustaining?
mustn't she have been sustaining?
mustn't we have been sustaining?
mustn't you have been sustaining?
mustn't they have been sustaining?