I could lighten you could lighten she could lighten we could lighten you could lighten they could lighten
V-ing form
I could be lightening you could be lightening she could be lightening we could be lightening you could be lightening they could be lightening
Perfect
I could have lightened you could have lightened she 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 she 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 she 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 she 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 she 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 she 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 she lighten? could we lighten? could you lighten? could they lighten?
V-ing form
could I be lightening? could you be lightening? could she be lightening? could we be lightening? could you be lightening? could they be lightening?
Perfect
could I have lightened? could you have lightened? could she 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 she 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 she 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 she 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 she 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 she have been lightening? couldn't we have been lightening? couldn't you have been lightening? couldn't they have been lightening?