I could straighten you could straighten he could straighten we could straighten you could straighten they could straighten
V-ing form
I could be straightening you could be straightening he could be straightening we could be straightening you could be straightening they could be straightening
Perfect
I could have straightened you could have straightened he could have straightened we could have straightened you could have straightened they could have straightened
V-ing perfect
I could have been straightening you could have been straightening he could have been straightening we could have been straightening you could have been straightening they could have been straightening
Negation
Simple form
I could not straighten you could not straighten he could not straighten we could not straighten you could not straighten they could not straighten
V-ing form
I could not be straightening you could not be straightening he could not be straightening we could not be straightening you could not be straightening they could not be straightening
Perfect
I could not have straightened you could not have straightened he could not have straightened we could not have straightened you could not have straightened they could not have straightened
V-ing perfect
I could not have been straightening you could not have been straightening he could not have been straightening we could not have been straightening you could not have been straightening they could not have been straightening
Interrogative form
Simple form
could I straighten? could you straighten? could he straighten? could we straighten? could you straighten? could they straighten?
V-ing form
could I be straightening? could you be straightening? could he be straightening? could we be straightening? could you be straightening? could they be straightening?
Perfect
could I have straightened? could you have straightened? could he have straightened? could we have straightened? could you have straightened? could they have straightened?
V-ing perfect
could I have been straightening? could you have been straightening? could he have been straightening? could we have been straightening? could you have been straightening? could they have been straightening?
Interro-negative form
Simple form
could I not straighten? could you not straighten? could he not straighten? could we not straighten? could you not straighten? could they not straighten?
V-ing form
could I not be straightening? could you not be straightening? could he not be straightening? could we not be straightening? could you not be straightening? could they not be straightening?
Perfect
could I not have straightened? could you not have straightened? could he not have straightened? could we not have straightened? could you not have straightened? could they not have straightened?
V-ing perfect
could I not have been straightening? could you not have been straightening? could he not have been straightening? could we not have been straightening? could you not have been straightening? could they not have been straightening?