I must countersink you must countersink she must countersink we must countersink you must countersink they must countersink
V-ing form
I must be countersinking you must be countersinking she must be countersinking we must be countersinking you must be countersinking they must be countersinking
Perfect
I must have countersunk you must have countersunk she must have countersunk we must have countersunk you must have countersunk they must have countersunk
V-ing perfect
I must have been countersinking you must have been countersinking she must have been countersinking we must have been countersinking you must have been countersinking they must have been countersinking
Negation
Simple form
I mustn't countersink you mustn't countersink she mustn't countersink we mustn't countersink you mustn't countersink they mustn't countersink
V-ing form
I mustn't be countersinking you mustn't be countersinking she mustn't be countersinking we mustn't be countersinking you mustn't be countersinking they mustn't be countersinking
Perfect
I mustn't have countersunk you mustn't have countersunk she mustn't have countersunk we mustn't have countersunk you mustn't have countersunk they mustn't have countersunk
V-ing perfect
I mustn't have been countersinking you mustn't have been countersinking she mustn't have been countersinking we mustn't have been countersinking you mustn't have been countersinking they mustn't have been countersinking
Interrogative form
Simple form
must I countersink? must you countersink? must she countersink? must we countersink? must you countersink? must they countersink?
V-ing form
must I be countersinking? must you be countersinking? must she be countersinking? must we be countersinking? must you be countersinking? must they be countersinking?
Perfect
must I have countersunk? must you have countersunk? must she have countersunk? must we have countersunk? must you have countersunk? must they have countersunk?
V-ing perfect
must I have been countersinking? must you have been countersinking? must she have been countersinking? must we have been countersinking? must you have been countersinking? must they have been countersinking?
Interro-negative form
Simple form
mustn't I countersink? mustn't you countersink? mustn't she countersink? mustn't we countersink? mustn't you countersink? mustn't they countersink?
V-ing form
mustn't I be countersinking? mustn't you be countersinking? mustn't she be countersinking? mustn't we be countersinking? mustn't you be countersinking? mustn't they be countersinking?
Perfect
mustn't I have countersunk? mustn't you have countersunk? mustn't she have countersunk? mustn't we have countersunk? mustn't you have countersunk? mustn't they have countersunk?
V-ing perfect
mustn't I have been countersinking? mustn't you have been countersinking? mustn't she have been countersinking? mustn't we have been countersinking? mustn't you have been countersinking? mustn't they have been countersinking?