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