English verb conjugation
MUST UNDERPIN

Regular verb: underpin - underpinned - underpinned

Affirmation

Simple form	V-ing form
I must underpin you must underpin he must underpin we must underpin you must underpin they must underpin	I must be underpinning you must be underpinning he must be underpinning we must be underpinning you must be underpinning they must be underpinning
Perfect	V-ing perfect
I must have underpinned you must have underpinned he must have underpinned we must have underpinned you must have underpinned they must have underpinned	I must have been underpinning you must have been underpinning he must have been underpinning we must have been underpinning you must have been underpinning they must have been underpinning

Negation

Simple form	V-ing form
I mustn't underpin you mustn't underpin he mustn't underpin we mustn't underpin you mustn't underpin they mustn't underpin	I mustn't be underpinning you mustn't be underpinning he mustn't be underpinning we mustn't be underpinning you mustn't be underpinning they mustn't be underpinning
Perfect	V-ing perfect
I mustn't have underpinned you mustn't have underpinned he mustn't have underpinned we mustn't have underpinned you mustn't have underpinned they mustn't have underpinned	I mustn't have been underpinning you mustn't have been underpinning he mustn't have been underpinning we mustn't have been underpinning you mustn't have been underpinning they mustn't have been underpinning

Interrogative form

Simple form	V-ing form
must I underpin? must you underpin? must he underpin? must we underpin? must you underpin? must they underpin?	must I be underpinning? must you be underpinning? must he be underpinning? must we be underpinning? must you be underpinning? must they be underpinning?
Perfect	V-ing perfect
must I have underpinned? must you have underpinned? must he have underpinned? must we have underpinned? must you have underpinned? must they have underpinned?	must I have been underpinning? must you have been underpinning? must he have been underpinning? must we have been underpinning? must you have been underpinning? must they have been underpinning?

Interro-negative form

Simple form	V-ing form
mustn't I underpin? mustn't you underpin? mustn't he underpin? mustn't we underpin? mustn't you underpin? mustn't they underpin?	mustn't I be underpinning? mustn't you be underpinning? mustn't he be underpinning? mustn't we be underpinning? mustn't you be underpinning? mustn't they be underpinning?
Perfect	V-ing perfect
mustn't I have underpinned? mustn't you have underpinned? mustn't he have underpinned? mustn't we have underpinned? mustn't you have underpinned? mustn't they have underpinned?	mustn't I have been underpinning? mustn't you have been underpinning? mustn't he have been underpinning? mustn't we have been underpinning? mustn't you have been underpinning? mustn't they have been underpinning?