I must gain you must gain he must gain we must gain you must gain they must gain
V-ing form
I must be gaining you must be gaining he must be gaining we must be gaining you must be gaining they must be gaining
Perfect
I must have gained you must have gained he must have gained we must have gained you must have gained they must have gained
V-ing perfect
I must have been gaining you must have been gaining he must have been gaining we must have been gaining you must have been gaining they must have been gaining
Negation
Simple form
I must not gain you must not gain he must not gain we must not gain you must not gain they must not gain
V-ing form
I must not be gaining you must not be gaining he must not be gaining we must not be gaining you must not be gaining they must not be gaining
Perfect
I must not have gained you must not have gained he must not have gained we must not have gained you must not have gained they must not have gained
V-ing perfect
I must not have been gaining you must not have been gaining he must not have been gaining we must not have been gaining you must not have been gaining they must not have been gaining
Interrogative form
Simple form
must I gain? must you gain? must he gain? must we gain? must you gain? must they gain?
V-ing form
must I be gaining? must you be gaining? must he be gaining? must we be gaining? must you be gaining? must they be gaining?
Perfect
must I have gained? must you have gained? must he have gained? must we have gained? must you have gained? must they have gained?
V-ing perfect
must I have been gaining? must you have been gaining? must he have been gaining? must we have been gaining? must you have been gaining? must they have been gaining?
Interro-negative form
Simple form
must I not gain? must you not gain? must he not gain? must we not gain? must you not gain? must they not gain?
V-ing form
must I not be gaining? must you not be gaining? must he not be gaining? must we not be gaining? must you not be gaining? must they not be gaining?
Perfect
must I not have gained? must you not have gained? must he not have gained? must we not have gained? must you not have gained? must they not have gained?
V-ing perfect
must I not have been gaining? must you not have been gaining? must he not have been gaining? must we not have been gaining? must you not have been gaining? must they not have been gaining?