could undulate
Regular verb: undulate - undulated- undulated

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could undulate
you could undulate
he could undulate
we could undulate
you could undulate
they could undulate 	I could be undulating
you could be undulating
he could be undulating
we could be undulating
you could be undulating
they could be undulating	I could have undulated
you could have undulated
he 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
he 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 could not undulate
you could not undulate
he could not undulate
we could not undulate
you could not undulate
they could not undulate 	I could not be undulating
you could not be undulating
he could not be undulating
we could not be undulating
you could not be undulating
they could not be undulating	I could not have undulated
you could not have undulated
he could not have undulated
we could not have undulated
you could not have undulated
they could not have undulated	I could not have been undulating
you could not have been undulating
he could not have been undulating
we could not have been undulating
you could not have been undulating
they could not have been undulating	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I undulate?
could you undulate?
could he undulate?
could we undulate?
could you undulate?
could they undulate? 	could I be undulating?
could you be undulating?
could he be undulating?
could we be undulating?
could you be undulating?
could they be undulating? 	could I have undulated?
could you have undulated?
could he 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 he 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 	
could I not undulate?
could you not undulate?
could he not undulate?
could we not undulate?
could you not undulate?
could they not undulate? 	could I not be undulating?
could you not be undulating?
could he not be undulating?
could we not be undulating?
could you not be undulating?
could they not be undulating? 	could I not have undulated?
could you not have undulated?
could he not have undulated?
could we not have undulated?
could you not have undulated?
could they not have undulated? 	could I not have been undulating?
could you not have been undulating?
could he not have been undulating?
could we not have been undulating?
could you not have been undulating?
could they not have been undulating?