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