English verb conjugation
COULD MUTTER

Regular verb: mutter - muttered - muttered

Affirmation

Simple form	V-ing form
I could mutter you could mutter he could mutter we could mutter you could mutter they could mutter	I could be muttering you could be muttering he could be muttering we could be muttering you could be muttering they could be muttering
Perfect	V-ing perfect
I could have muttered you could have muttered he could have muttered we could have muttered you could have muttered they could have muttered	I could have been muttering you could have been muttering he could have been muttering we could have been muttering you could have been muttering they could have been muttering

Negation

Simple form	V-ing form
I could not mutter you could not mutter he could not mutter we could not mutter you could not mutter they could not mutter	I could not be muttering you could not be muttering he could not be muttering we could not be muttering you could not be muttering they could not be muttering
Perfect	V-ing perfect
I could not have muttered you could not have muttered he could not have muttered we could not have muttered you could not have muttered they could not have muttered	I could not have been muttering you could not have been muttering he could not have been muttering we could not have been muttering you could not have been muttering they could not have been muttering

Interrogative form

Simple form	V-ing form
could I mutter? could you mutter? could he mutter? could we mutter? could you mutter? could they mutter?	could I be muttering? could you be muttering? could he be muttering? could we be muttering? could you be muttering? could they be muttering?
Perfect	V-ing perfect
could I have muttered? could you have muttered? could he have muttered? could we have muttered? could you have muttered? could they have muttered?	could I have been muttering? could you have been muttering? could he have been muttering? could we have been muttering? could you have been muttering? could they have been muttering?

Interro-negative form

Simple form	V-ing form
could I not mutter? could you not mutter? could he not mutter? could we not mutter? could you not mutter? could they not mutter?	could I not be muttering? could you not be muttering? could he not be muttering? could we not be muttering? could you not be muttering? could they not be muttering?
Perfect	V-ing perfect
could I not have muttered? could you not have muttered? could he not have muttered? could we not have muttered? could you not have muttered? could they not have muttered?	could I not have been muttering? could you not have been muttering? could he not have been muttering? could we not have been muttering? could you not have been muttering? could they not have been muttering?