must backfire
Regular verb: backfire - backfired- backfired

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must backfire
you must backfire
he must backfire
we must backfire
you must backfire
they must backfire 	I must be backfiring
you must be backfiring
he must be backfiring
we must be backfiring
you must be backfiring
they must be backfiring	I must have backfired
you must have backfired
he must have backfired
we must have backfired
you must have backfired
they must have backfired	I must have been backfiring
you must have been backfiring
he must have been backfiring
we must have been backfiring
you must have been backfiring
they must have been backfiring	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must not backfire
you must not backfire
he must not backfire
we must not backfire
you must not backfire
they must not backfire 	I must not be backfiring
you must not be backfiring
he must not be backfiring
we must not be backfiring
you must not be backfiring
they must not be backfiring	I must not have backfired
you must not have backfired
he must not have backfired
we must not have backfired
you must not have backfired
they must not have backfired	I must not have been backfiring
you must not have been backfiring
he must not have been backfiring
we must not have been backfiring
you must not have been backfiring
they must not have been backfiring	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I backfire?
must you backfire?
must he backfire?
must we backfire?
must you backfire?
must they backfire? 	must I be backfiring?
must you be backfiring?
must he be backfiring?
must we be backfiring?
must you be backfiring?
must they be backfiring? 	must I have backfired?
must you have backfired?
must he have backfired?
must we have backfired?
must you have backfired?
must they have backfired? 	must I have been backfiring?
must you have been backfiring?
must he have been backfiring?
must we have been backfiring?
must you have been backfiring?
must they have been backfiring? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I not backfire?
must you not backfire?
must he not backfire?
must we not backfire?
must you not backfire?
must they not backfire? 	must I not be backfiring?
must you not be backfiring?
must he not be backfiring?
must we not be backfiring?
must you not be backfiring?
must they not be backfiring? 	must I not have backfired?
must you not have backfired?
must he not have backfired?
must we not have backfired?
must you not have backfired?
must they not have backfired? 	must I not have been backfiring?
must you not have been backfiring?
must he not have been backfiring?
must we not have been backfiring?
must you not have been backfiring?
must they not have been backfiring?