English verb conjugation
COULD STEM

Regular verb: stem - stemmed - stemmed

Affirmation

Simple form	V-ing form
I could stem you could stem she could stem we could stem you could stem they could stem	I could be stemming you could be stemming she could be stemming we could be stemming you could be stemming they could be stemming
Perfect	V-ing perfect
I could have stemmed you could have stemmed she could have stemmed we could have stemmed you could have stemmed they could have stemmed	I could have been stemming you could have been stemming she could have been stemming we could have been stemming you could have been stemming they could have been stemming

Negation

Simple form	V-ing form
I couldn't stem you couldn't stem she couldn't stem we couldn't stem you couldn't stem they couldn't stem	I couldn't be stemming you couldn't be stemming she couldn't be stemming we couldn't be stemming you couldn't be stemming they couldn't be stemming
Perfect	V-ing perfect
I couldn't have stemmed you couldn't have stemmed she couldn't have stemmed we couldn't have stemmed you couldn't have stemmed they couldn't have stemmed	I couldn't have been stemming you couldn't have been stemming she couldn't have been stemming we couldn't have been stemming you couldn't have been stemming they couldn't have been stemming

Interrogative form

Simple form	V-ing form
could I stem? could you stem? could she stem? could we stem? could you stem? could they stem?	could I be stemming? could you be stemming? could she be stemming? could we be stemming? could you be stemming? could they be stemming?
Perfect	V-ing perfect
could I have stemmed? could you have stemmed? could she have stemmed? could we have stemmed? could you have stemmed? could they have stemmed?	could I have been stemming? could you have been stemming? could she have been stemming? could we have been stemming? could you have been stemming? could they have been stemming?

Interro-negative form

Simple form	V-ing form
couldn't I stem? couldn't you stem? couldn't she stem? couldn't we stem? couldn't you stem? couldn't they stem?	couldn't I be stemming? couldn't you be stemming? couldn't she be stemming? couldn't we be stemming? couldn't you be stemming? couldn't they be stemming?
Perfect	V-ing perfect
couldn't I have stemmed? couldn't you have stemmed? couldn't she have stemmed? couldn't we have stemmed? couldn't you have stemmed? couldn't they have stemmed?	couldn't I have been stemming? couldn't you have been stemming? couldn't she have been stemming? couldn't we have been stemming? couldn't you have been stemming? couldn't they have been stemming?