I could highlight you could highlight she could highlight we could highlight you could highlight they could highlight
V-ing form
I could be highlighting you could be highlighting she could be highlighting we could be highlighting you could be highlighting they could be highlighting
Perfect
I could have highlighted you could have highlighted she 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 she 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 she 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 she 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 she 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 she 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 she highlight? could we highlight? could you highlight? could they highlight?
V-ing form
could I be highlighting? could you be highlighting? could she be highlighting? could we be highlighting? could you be highlighting? could they be highlighting?
Perfect
could I have highlighted? could you have highlighted? could she 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 she 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 she 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 she 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 she 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 she have been highlighting? couldn't we have been highlighting? couldn't you have been highlighting? couldn't they have been highlighting?