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