could undulate
Regular verb: undulate - undulated- undulated

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could undulate
you could undulate
she could undulate
we could undulate
you could undulate
they could undulate 	I could be undulating
you could be undulating
she could be undulating
we could be undulating
you could be undulating
they could be undulating	I could have undulated
you could have undulated
she could have undulated
we could have undulated
you could have undulated
they could have undulated	I could have been undulating
you could have been undulating
she could have been undulating
we could have been undulating
you could have been undulating
they could have been undulating	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't undulate
you couldn't undulate
she couldn't undulate
we couldn't undulate
you couldn't undulate
they couldn't undulate 	I couldn't be undulating
you couldn't be undulating
she couldn't be undulating
we couldn't be undulating
you couldn't be undulating
they couldn't be undulating	I couldn't have undulated
you couldn't have undulated
she couldn't have undulated
we couldn't have undulated
you couldn't have undulated
they couldn't have undulated	I couldn't have been undulating
you couldn't have been undulating
she couldn't have been undulating
we couldn't have been undulating
you couldn't have been undulating
they couldn't have been undulating	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I undulate?
could you undulate?
could she undulate?
could we undulate?
could you undulate?
could they undulate? 	could I be undulating?
could you be undulating?
could she be undulating?
could we be undulating?
could you be undulating?
could they be undulating? 	could I have undulated?
could you have undulated?
could she have undulated?
could we have undulated?
could you have undulated?
could they have undulated? 	could I have been undulating?
could you have been undulating?
could she have been undulating?
could we have been undulating?
could you have been undulating?
could they have been undulating? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I undulate?
couldn't you undulate?
couldn't she undulate?
couldn't we undulate?
couldn't you undulate?
couldn't they undulate? 	couldn't I be undulating?
couldn't you be undulating?
couldn't she be undulating?
couldn't we be undulating?
couldn't you be undulating?
couldn't they be undulating? 	couldn't I have undulated?
couldn't you have undulated?
couldn't she have undulated?
couldn't we have undulated?
couldn't you have undulated?
couldn't they have undulated? 	couldn't I have been undulating?
couldn't you have been undulating?
couldn't she have been undulating?
couldn't we have been undulating?
couldn't you have been undulating?
couldn't they have been undulating?