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