I must arch you must arch she must arch we must arch you must arch they must arch
V-ing form
I must be arching you must be arching she must be arching we must be arching you must be arching they must be arching
Perfect
I must have arched you must have arched she must have arched we must have arched you must have arched they must have arched
V-ing perfect
I must have been arching you must have been arching she must have been arching we must have been arching you must have been arching they must have been arching
Negation
Simple form
I must not arch you must not arch she must not arch we must not arch you must not arch they must not arch
V-ing form
I must not be arching you must not be arching she must not be arching we must not be arching you must not be arching they must not be arching
Perfect
I must not have arched you must not have arched she must not have arched we must not have arched you must not have arched they must not have arched
V-ing perfect
I must not have been arching you must not have been arching she must not have been arching we must not have been arching you must not have been arching they must not have been arching
Interrogative form
Simple form
must I arch? must you arch? must she arch? must we arch? must you arch? must they arch?
V-ing form
must I be arching? must you be arching? must she be arching? must we be arching? must you be arching? must they be arching?
Perfect
must I have arched? must you have arched? must she have arched? must we have arched? must you have arched? must they have arched?
V-ing perfect
must I have been arching? must you have been arching? must she have been arching? must we have been arching? must you have been arching? must they have been arching?
Interro-negative form
Simple form
must I not arch? must you not arch? must she not arch? must we not arch? must you not arch? must they not arch?
V-ing form
must I not be arching? must you not be arching? must she not be arching? must we not be arching? must you not be arching? must they not be arching?
Perfect
must I not have arched? must you not have arched? must she not have arched? must we not have arched? must you not have arched? must they not have arched?
V-ing perfect
must I not have been arching? must you not have been arching? must she not have been arching? must we not have been arching? must you not have been arching? must they not have been arching?