can backfill
Regular verb: backfill - backfilled- backfilled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I can backfill
you can backfill
he can backfill
we can backfill
you can backfill
they can backfill 	I can be backfilling
you can be backfilling
he can be backfilling
we can be backfilling
you can be backfilling
they can be backfilling	I can have backfilled
you can have backfilled
he can have backfilled
we can have backfilled
you can have backfilled
they can have backfilled	I can have been backfilling
you can have been backfilling
he can have been backfilling
we can have been backfilling
you can have been backfilling
they can have been backfilling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I cannot backfill
you cannot backfill
he cannot backfill
we cannot backfill
you cannot backfill
they cannot backfill 	I cannot be backfilling
you cannot be backfilling
he cannot be backfilling
we cannot be backfilling
you cannot be backfilling
they cannot be backfilling	I cannot have backfilled
you cannot have backfilled
he cannot have backfilled
we cannot have backfilled
you cannot have backfilled
they cannot have backfilled	I cannot have been backfilling
you cannot have been backfilling
he cannot have been backfilling
we cannot have been backfilling
you cannot have been backfilling
they cannot have been backfilling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can I backfill?
can you backfill?
can he backfill?
can we backfill?
can you backfill?
can they backfill? 	can I be backfilling?
can you be backfilling?
can he be backfilling?
can we be backfilling?
can you be backfilling?
can they be backfilling? 	can I have backfilled?
can you have backfilled?
can he have backfilled?
can we have backfilled?
can you have backfilled?
can they have backfilled? 	can I have been backfilling?
can you have been backfilling?
can he have been backfilling?
can we have been backfilling?
can you have been backfilling?
can they have been backfilling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can I not backfill?
can you not backfill?
can he not backfill?
can we not backfill?
can you not backfill?
can they not backfill? 	can I not be backfilling?
can you not be backfilling?
can he not be backfilling?
can we not be backfilling?
can you not be backfilling?
can they not be backfilling? 	can I not have backfilled?
can you not have backfilled?
can he not have backfilled?
can we not have backfilled?
can you not have backfilled?
can they not have backfilled? 	can I not have been backfilling?
can you not have been backfilling?
can he not have been backfilling?
can we not have been backfilling?
can you not have been backfilling?
can they not have been backfilling?