I could masturbate you could masturbate he could masturbate we could masturbate you could masturbate they could masturbate
V-ing form
I could be masturbating you could be masturbating he could be masturbating we could be masturbating you could be masturbating they could be masturbating
Perfect
I could have masturbated you could have masturbated he could have masturbated we could have masturbated you could have masturbated they could have masturbated
V-ing perfect
I could have been masturbating you could have been masturbating he could have been masturbating we could have been masturbating you could have been masturbating they could have been masturbating
Negation
Simple form
I could not masturbate you could not masturbate he could not masturbate we could not masturbate you could not masturbate they could not masturbate
V-ing form
I could not be masturbating you could not be masturbating he could not be masturbating we could not be masturbating you could not be masturbating they could not be masturbating
Perfect
I could not have masturbated you could not have masturbated he could not have masturbated we could not have masturbated you could not have masturbated they could not have masturbated
V-ing perfect
I could not have been masturbating you could not have been masturbating he could not have been masturbating we could not have been masturbating you could not have been masturbating they could not have been masturbating
Interrogative form
Simple form
could I masturbate? could you masturbate? could he masturbate? could we masturbate? could you masturbate? could they masturbate?
V-ing form
could I be masturbating? could you be masturbating? could he be masturbating? could we be masturbating? could you be masturbating? could they be masturbating?
Perfect
could I have masturbated? could you have masturbated? could he have masturbated? could we have masturbated? could you have masturbated? could they have masturbated?
V-ing perfect
could I have been masturbating? could you have been masturbating? could he have been masturbating? could we have been masturbating? could you have been masturbating? could they have been masturbating?
Interro-negative form
Simple form
could I not masturbate? could you not masturbate? could he not masturbate? could we not masturbate? could you not masturbate? could they not masturbate?
V-ing form
could I not be masturbating? could you not be masturbating? could he not be masturbating? could we not be masturbating? could you not be masturbating? could they not be masturbating?
Perfect
could I not have masturbated? could you not have masturbated? could he not have masturbated? could we not have masturbated? could you not have masturbated? could they not have masturbated?
V-ing perfect
could I not have been masturbating? could you not have been masturbating? could he not have been masturbating? could we not have been masturbating? could you not have been masturbating? could they not have been masturbating?