I can tighten you can tighten he can tighten we can tighten you can tighten they can tighten
V-ing form
I can be tightening you can be tightening he can be tightening we can be tightening you can be tightening they can be tightening
Perfect
I can have tightened you can have tightened he can have tightened we can have tightened you can have tightened they can have tightened
V-ing perfect
I can have been tightening you can have been tightening he can have been tightening we can have been tightening you can have been tightening they can have been tightening
Negation
Simple form
I can't tighten you can't tighten he can't tighten we can't tighten you can't tighten they can't tighten
V-ing form
I can't be tightening you can't be tightening he can't be tightening we can't be tightening you can't be tightening they can't be tightening
Perfect
I can't have tightened you can't have tightened he can't have tightened we can't have tightened you can't have tightened they can't have tightened
V-ing perfect
I can't have been tightening you can't have been tightening he can't have been tightening we can't have been tightening you can't have been tightening they can't have been tightening
Interrogative form
Simple form
can I tighten? can you tighten? can he tighten? can we tighten? can you tighten? can they tighten?
V-ing form
can I be tightening? can you be tightening? can he be tightening? can we be tightening? can you be tightening? can they be tightening?
Perfect
can I have tightened? can you have tightened? can he have tightened? can we have tightened? can you have tightened? can they have tightened?
V-ing perfect
can I have been tightening? can you have been tightening? can he have been tightening? can we have been tightening? can you have been tightening? can they have been tightening?
Interro-negative form
Simple form
can't I tighten? can't you tighten? can't he tighten? can't we tighten? can't you tighten? can't they tighten?
V-ing form
can't I be tightening? can't you be tightening? can't he be tightening? can't we be tightening? can't you be tightening? can't they be tightening?
Perfect
can't I have tightened? can't you have tightened? can't he have tightened? can't we have tightened? can't you have tightened? can't they have tightened?
V-ing perfect
can't I have been tightening? can't you have been tightening? can't he have been tightening? can't we have been tightening? can't you have been tightening? can't they have been tightening?