I must base you must base he must base we must base you must base they must base
V-ing form
I must be basing you must be basing he must be basing we must be basing you must be basing they must be basing
Perfect
I must have based you must have based he must have based we must have based you must have based they must have based
V-ing perfect
I must have been basing you must have been basing he must have been basing we must have been basing you must have been basing they must have been basing
Negation
Simple form
I mustn't base you mustn't base he mustn't base we mustn't base you mustn't base they mustn't base
V-ing form
I mustn't be basing you mustn't be basing he mustn't be basing we mustn't be basing you mustn't be basing they mustn't be basing
Perfect
I mustn't have based you mustn't have based he mustn't have based we mustn't have based you mustn't have based they mustn't have based
V-ing perfect
I mustn't have been basing you mustn't have been basing he mustn't have been basing we mustn't have been basing you mustn't have been basing they mustn't have been basing
Interrogative form
Simple form
must I base? must you base? must he base? must we base? must you base? must they base?
V-ing form
must I be basing? must you be basing? must he be basing? must we be basing? must you be basing? must they be basing?
Perfect
must I have based? must you have based? must he have based? must we have based? must you have based? must they have based?
V-ing perfect
must I have been basing? must you have been basing? must he have been basing? must we have been basing? must you have been basing? must they have been basing?
Interro-negative form
Simple form
mustn't I base? mustn't you base? mustn't he base? mustn't we base? mustn't you base? mustn't they base?
V-ing form
mustn't I be basing? mustn't you be basing? mustn't he be basing? mustn't we be basing? mustn't you be basing? mustn't they be basing?
Perfect
mustn't I have based? mustn't you have based? mustn't he have based? mustn't we have based? mustn't you have based? mustn't they have based?
V-ing perfect
mustn't I have been basing? mustn't you have been basing? mustn't he have been basing? mustn't we have been basing? mustn't you have been basing? mustn't they have been basing?