I can straighten you can straighten she can straighten we can straighten you can straighten they can straighten
V-ing form
I can be straightening you can be straightening she can be straightening we can be straightening you can be straightening they can be straightening
Perfect
I can have straightened you can have straightened she can have straightened we can have straightened you can have straightened they can have straightened
V-ing perfect
I can have been straightening you can have been straightening she can have been straightening we can have been straightening you can have been straightening they can have been straightening
Negation
Simple form
I can't straighten you can't straighten she can't straighten we can't straighten you can't straighten they can't straighten
V-ing form
I can't be straightening you can't be straightening she can't be straightening we can't be straightening you can't be straightening they can't be straightening
Perfect
I can't have straightened you can't have straightened she can't have straightened we can't have straightened you can't have straightened they can't have straightened
V-ing perfect
I can't have been straightening you can't have been straightening she can't have been straightening we can't have been straightening you can't have been straightening they can't have been straightening
Interrogative form
Simple form
can I straighten? can you straighten? can she straighten? can we straighten? can you straighten? can they straighten?
V-ing form
can I be straightening? can you be straightening? can she be straightening? can we be straightening? can you be straightening? can they be straightening?
Perfect
can I have straightened? can you have straightened? can she have straightened? can we have straightened? can you have straightened? can they have straightened?
V-ing perfect
can I have been straightening? can you have been straightening? can she have been straightening? can we have been straightening? can you have been straightening? can they have been straightening?
Interro-negative form
Simple form
can't I straighten? can't you straighten? can't she straighten? can't we straighten? can't you straighten? can't they straighten?
V-ing form
can't I be straightening? can't you be straightening? can't she be straightening? can't we be straightening? can't you be straightening? can't they be straightening?
Perfect
can't I have straightened? can't you have straightened? can't she have straightened? can't we have straightened? can't you have straightened? can't they have straightened?
V-ing perfect
can't I have been straightening? can't you have been straightening? can't she have been straightening? can't we have been straightening? can't you have been straightening? can't they have been straightening?