Warning, this verb may not exist. Conjugation is given as example.
Affirmation
Simple form
I could mar mar you could mar mar he could mar mar we could mar mar you could mar mar they could mar mar
V-ing form
I could be mar maring you could be mar maring he could be mar maring we could be mar maring you could be mar maring they could be mar maring
Perfect
I could have mar mared you could have mar mared he could have mar mared we could have mar mared you could have mar mared they could have mar mared
V-ing perfect
I could have been mar maring you could have been mar maring he could have been mar maring we could have been mar maring you could have been mar maring they could have been mar maring
Negation
Simple form
I couldn't mar mar you couldn't mar mar he couldn't mar mar we couldn't mar mar you couldn't mar mar they couldn't mar mar
V-ing form
I couldn't be mar maring you couldn't be mar maring he couldn't be mar maring we couldn't be mar maring you couldn't be mar maring they couldn't be mar maring
Perfect
I couldn't have mar mared you couldn't have mar mared he couldn't have mar mared we couldn't have mar mared you couldn't have mar mared they couldn't have mar mared
V-ing perfect
I couldn't have been mar maring you couldn't have been mar maring he couldn't have been mar maring we couldn't have been mar maring you couldn't have been mar maring they couldn't have been mar maring
Interrogative form
Simple form
could I mar mar? could you mar mar? could he mar mar? could we mar mar? could you mar mar? could they mar mar?
V-ing form
could I be mar maring? could you be mar maring? could he be mar maring? could we be mar maring? could you be mar maring? could they be mar maring?
Perfect
could I have mar mared? could you have mar mared? could he have mar mared? could we have mar mared? could you have mar mared? could they have mar mared?
V-ing perfect
could I have been mar maring? could you have been mar maring? could he have been mar maring? could we have been mar maring? could you have been mar maring? could they have been mar maring?
Interro-negative form
Simple form
couldn't I mar mar? couldn't you mar mar? couldn't he mar mar? couldn't we mar mar? couldn't you mar mar? couldn't they mar mar?
V-ing form
couldn't I be mar maring? couldn't you be mar maring? couldn't he be mar maring? couldn't we be mar maring? couldn't you be mar maring? couldn't they be mar maring?
Perfect
couldn't I have mar mared? couldn't you have mar mared? couldn't he have mar mared? couldn't we have mar mared? couldn't you have mar mared? couldn't they have mar mared?
V-ing perfect
couldn't I have been mar maring? couldn't you have been mar maring? couldn't he have been mar maring? couldn't we have been mar maring? couldn't you have been mar maring? couldn't they have been mar maring?