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 could not sweeten you could not sweeten he could not sweeten we could not sweeten you could not sweeten they could not sweeten
V-ing form
I could not be sweetening you could not be sweetening he could not be sweetening we could not be sweetening you could not be sweetening they could not be sweetening
Perfect
I could not have sweetened you could not have sweetened he could not have sweetened we could not have sweetened you could not have sweetened they could not have sweetened
V-ing perfect
I could not have been sweetening you could not have been sweetening he could not have been sweetening we could not have been sweetening you could not have been sweetening they could not 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
could I not sweeten? could you not sweeten? could he not sweeten? could we not sweeten? could you not sweeten? could they not sweeten?
V-ing form
could I not be sweetening? could you not be sweetening? could he not be sweetening? could we not be sweetening? could you not be sweetening? could they not be sweetening?
Perfect
could I not have sweetened? could you not have sweetened? could he not have sweetened? could we not have sweetened? could you not have sweetened? could they not have sweetened?
V-ing perfect
could I not have been sweetening? could you not have been sweetening? could he not have been sweetening? could we not have been sweetening? could you not have been sweetening? could they not have been sweetening?