can stem
Regular verb: stem - stemmed- stemmed

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

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

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

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