English verb conjugation
MUST CRUMBLE

Regular verb: crumble - crumbled - crumbled

Affirmation

Simple form	V-ing form
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
Perfect	V-ing perfect
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

Negation

Simple form	V-ing form
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
Perfect	V-ing perfect
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

Interrogative form

Simple form	V-ing form
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?
Perfect	V-ing perfect
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?

Interro-negative form

Simple form	V-ing form
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?
Perfect	V-ing perfect
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?