must ruin
Regular verb: ruin - ruined- ruined

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must ruin
you must ruin
he must ruin
we must ruin
you must ruin
they must ruin 	I must be ruining
you must be ruining
he must be ruining
we must be ruining
you must be ruining
they must be ruining	I must have ruined
you must have ruined
he must have ruined
we must have ruined
you must have ruined
they must have ruined	I must have been ruining
you must have been ruining
he must have been ruining
we must have been ruining
you must have been ruining
they must have been ruining	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't ruin
you mustn't ruin
he mustn't ruin
we mustn't ruin
you mustn't ruin
they mustn't ruin 	I mustn't be ruining
you mustn't be ruining
he mustn't be ruining
we mustn't be ruining
you mustn't be ruining
they mustn't be ruining	I mustn't have ruined
you mustn't have ruined
he mustn't have ruined
we mustn't have ruined
you mustn't have ruined
they mustn't have ruined	I mustn't have been ruining
you mustn't have been ruining
he mustn't have been ruining
we mustn't have been ruining
you mustn't have been ruining
they mustn't have been ruining	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I ruin?
must you ruin?
must he ruin?
must we ruin?
must you ruin?
must they ruin? 	must I be ruining?
must you be ruining?
must he be ruining?
must we be ruining?
must you be ruining?
must they be ruining? 	must I have ruined?
must you have ruined?
must he have ruined?
must we have ruined?
must you have ruined?
must they have ruined? 	must I have been ruining?
must you have been ruining?
must he have been ruining?
must we have been ruining?
must you have been ruining?
must they have been ruining? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I ruin?
mustn't you ruin?
mustn't he ruin?
mustn't we ruin?
mustn't you ruin?
mustn't they ruin? 	mustn't I be ruining?
mustn't you be ruining?
mustn't he be ruining?
mustn't we be ruining?
mustn't you be ruining?
mustn't they be ruining? 	mustn't I have ruined?
mustn't you have ruined?
mustn't he have ruined?
mustn't we have ruined?
mustn't you have ruined?
mustn't they have ruined? 	mustn't I have been ruining?
mustn't you have been ruining?
mustn't he have been ruining?
mustn't we have been ruining?
mustn't you have been ruining?
mustn't they have been ruining?