English verb conjugation
COULD UNDULATE

Regular verb: undulate - undulated - undulated

Affirmation

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