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