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