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