must crumble
Verbo regular: crumble - crumbled- crumbled

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must crumble
you must crumble
he must crumble
we must crumble
you must crumble
they must crumble 	I must be crumbling
you must be crumbling
he must be crumbling
we must be crumbling
you must be crumbling
they must be crumbling	I must have crumbled
you must have crumbled
he must have crumbled
we must have crumbled
you must have crumbled
they must have crumbled	I must have been crumbling
you must have been crumbling
he must have been crumbling
we must have been crumbling
you must have been crumbling
they must have been crumbling	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I mustn't crumble
you mustn't crumble
he mustn't crumble
we mustn't crumble
you mustn't crumble
they mustn't crumble 	I mustn't be crumbling
you mustn't be crumbling
he mustn't be crumbling
we mustn't be crumbling
you mustn't be crumbling
they mustn't be crumbling	I mustn't have crumbled
you mustn't have crumbled
he mustn't have crumbled
we mustn't have crumbled
you mustn't have crumbled
they mustn't have crumbled	I mustn't have been crumbling
you mustn't have been crumbling
he mustn't have been crumbling
we mustn't have been crumbling
you mustn't have been crumbling
they mustn't have been crumbling	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I crumble?
must you crumble?
must he crumble?
must we crumble?
must you crumble?
must they crumble? 	must I be crumbling?
must you be crumbling?
must he be crumbling?
must we be crumbling?
must you be crumbling?
must they be crumbling? 	must I have crumbled?
must you have crumbled?
must he have crumbled?
must we have crumbled?
must you have crumbled?
must they have crumbled? 	must I have been crumbling?
must you have been crumbling?
must he have been crumbling?
must we have been crumbling?
must you have been crumbling?
must they have been crumbling? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
mustn't I crumble?
mustn't you crumble?
mustn't he crumble?
mustn't we crumble?
mustn't you crumble?
mustn't they crumble? 	mustn't I be crumbling?
mustn't you be crumbling?
mustn't he be crumbling?
mustn't we be crumbling?
mustn't you be crumbling?
mustn't they be crumbling? 	mustn't I have crumbled?
mustn't you have crumbled?
mustn't he have crumbled?
mustn't we have crumbled?
mustn't you have crumbled?
mustn't they have crumbled? 	mustn't I have been crumbling?
mustn't you have been crumbling?
mustn't he have been crumbling?
mustn't we have been crumbling?
mustn't you have been crumbling?
mustn't they have been crumbling?