can understudy
Regular verb: understudy - understudied- understudied

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I can understudy
you can understudy
he can understudy
we can understudy
you can understudy
they can understudy 	I can be understudying
you can be understudying
he can be understudying
we can be understudying
you can be understudying
they can be understudying	I can have understudied
you can have understudied
he can have understudied
we can have understudied
you can have understudied
they can have understudied	I can have been understudying
you can have been understudying
he can have been understudying
we can have been understudying
you can have been understudying
they can have been understudying	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I can't understudy
you can't understudy
he can't understudy
we can't understudy
you can't understudy
they can't understudy 	I can't be understudying
you can't be understudying
he can't be understudying
we can't be understudying
you can't be understudying
they can't be understudying	I can't have understudied
you can't have understudied
he can't have understudied
we can't have understudied
you can't have understudied
they can't have understudied	I can't have been understudying
you can't have been understudying
he can't have been understudying
we can't have been understudying
you can't have been understudying
they can't have been understudying	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can I understudy?
can you understudy?
can he understudy?
can we understudy?
can you understudy?
can they understudy? 	can I be understudying?
can you be understudying?
can he be understudying?
can we be understudying?
can you be understudying?
can they be understudying? 	can I have understudied?
can you have understudied?
can he have understudied?
can we have understudied?
can you have understudied?
can they have understudied? 	can I have been understudying?
can you have been understudying?
can he have been understudying?
can we have been understudying?
can you have been understudying?
can they have been understudying? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can't I understudy?
can't you understudy?
can't he understudy?
can't we understudy?
can't you understudy?
can't they understudy? 	can't I be understudying?
can't you be understudying?
can't he be understudying?
can't we be understudying?
can't you be understudying?
can't they be understudying? 	can't I have understudied?
can't you have understudied?
can't he have understudied?
can't we have understudied?
can't you have understudied?
can't they have understudied? 	can't I have been understudying?
can't you have been understudying?
can't he have been understudying?
can't we have been understudying?
can't you have been understudying?
can't they have been understudying?