I can underline you can underline he can underline we can underline you can underline they can underline
V-ing form
I can be underlining you can be underlining he can be underlining we can be underlining you can be underlining they can be underlining
Perfect
I can have underlined you can have underlined he can have underlined we can have underlined you can have underlined they can have underlined
V-ing perfect
I can have been underlining you can have been underlining he can have been underlining we can have been underlining you can have been underlining they can have been underlining
Negation
Simple form
I can't underline you can't underline he can't underline we can't underline you can't underline they can't underline
V-ing form
I can't be underlining you can't be underlining he can't be underlining we can't be underlining you can't be underlining they can't be underlining
Perfect
I can't have underlined you can't have underlined he can't have underlined we can't have underlined you can't have underlined they can't have underlined
V-ing perfect
I can't have been underlining you can't have been underlining he can't have been underlining we can't have been underlining you can't have been underlining they can't have been underlining
Interrogative form
Simple form
can I underline? can you underline? can he underline? can we underline? can you underline? can they underline?
V-ing form
can I be underlining? can you be underlining? can he be underlining? can we be underlining? can you be underlining? can they be underlining?
Perfect
can I have underlined? can you have underlined? can he have underlined? can we have underlined? can you have underlined? can they have underlined?
V-ing perfect
can I have been underlining? can you have been underlining? can he have been underlining? can we have been underlining? can you have been underlining? can they have been underlining?
Interro-negative form
Simple form
can't I underline? can't you underline? can't he underline? can't we underline? can't you underline? can't they underline?
V-ing form
can't I be underlining? can't you be underlining? can't he be underlining? can't we be underlining? can't you be underlining? can't they be underlining?
Perfect
can't I have underlined? can't you have underlined? can't he have underlined? can't we have underlined? can't you have underlined? can't they have underlined?
V-ing perfect
can't I have been underlining? can't you have been underlining? can't he have been underlining? can't we have been underlining? can't you have been underlining? can't they have been underlining?