I could fulfill you could fulfill he could fulfill we could fulfill you could fulfill they could fulfill
V-ing form
I could be fulfilling you could be fulfilling he could be fulfilling we could be fulfilling you could be fulfilling they could be fulfilling
Perfect
I could have fulfilled you could have fulfilled he could have fulfilled we could have fulfilled you could have fulfilled they could have fulfilled
V-ing perfect
I could have been fulfilling you could have been fulfilling he could have been fulfilling we could have been fulfilling you could have been fulfilling they could have been fulfilling
Negation
Simple form
I couldn't fulfill you couldn't fulfill he couldn't fulfill we couldn't fulfill you couldn't fulfill they couldn't fulfill
V-ing form
I couldn't be fulfilling you couldn't be fulfilling he couldn't be fulfilling we couldn't be fulfilling you couldn't be fulfilling they couldn't be fulfilling
Perfect
I couldn't have fulfilled you couldn't have fulfilled he couldn't have fulfilled we couldn't have fulfilled you couldn't have fulfilled they couldn't have fulfilled
V-ing perfect
I couldn't have been fulfilling you couldn't have been fulfilling he couldn't have been fulfilling we couldn't have been fulfilling you couldn't have been fulfilling they couldn't have been fulfilling
Interrogative form
Simple form
could I fulfill? could you fulfill? could he fulfill? could we fulfill? could you fulfill? could they fulfill?
V-ing form
could I be fulfilling? could you be fulfilling? could he be fulfilling? could we be fulfilling? could you be fulfilling? could they be fulfilling?
Perfect
could I have fulfilled? could you have fulfilled? could he have fulfilled? could we have fulfilled? could you have fulfilled? could they have fulfilled?
V-ing perfect
could I have been fulfilling? could you have been fulfilling? could he have been fulfilling? could we have been fulfilling? could you have been fulfilling? could they have been fulfilling?
Interro-negative form
Simple form
couldn't I fulfill? couldn't you fulfill? couldn't he fulfill? couldn't we fulfill? couldn't you fulfill? couldn't they fulfill?
V-ing form
couldn't I be fulfilling? couldn't you be fulfilling? couldn't he be fulfilling? couldn't we be fulfilling? couldn't you be fulfilling? couldn't they be fulfilling?
Perfect
couldn't I have fulfilled? couldn't you have fulfilled? couldn't he have fulfilled? couldn't we have fulfilled? couldn't you have fulfilled? couldn't they have fulfilled?
V-ing perfect
couldn't I have been fulfilling? couldn't you have been fulfilling? couldn't he have been fulfilling? couldn't we have been fulfilling? couldn't you have been fulfilling? couldn't they have been fulfilling?