English verb conjugation
COULD PROP

Regular verb: prop - propped - propped

Affirmation

Simple form	V-ing form
I could prop you could prop he could prop we could prop you could prop they could prop	I could be propping you could be propping he could be propping we could be propping you could be propping they could be propping
Perfect	V-ing perfect
I could have propped you could have propped he could have propped we could have propped you could have propped they could have propped	I could have been propping you could have been propping he could have been propping we could have been propping you could have been propping they could have been propping

Negation

Simple form	V-ing form
I could not prop you could not prop he could not prop we could not prop you could not prop they could not prop	I could not be propping you could not be propping he could not be propping we could not be propping you could not be propping they could not be propping
Perfect	V-ing perfect
I could not have propped you could not have propped he could not have propped we could not have propped you could not have propped they could not have propped	I could not have been propping you could not have been propping he could not have been propping we could not have been propping you could not have been propping they could not have been propping

Interrogative form

Simple form	V-ing form
could I prop? could you prop? could he prop? could we prop? could you prop? could they prop?	could I be propping? could you be propping? could he be propping? could we be propping? could you be propping? could they be propping?
Perfect	V-ing perfect
could I have propped? could you have propped? could he have propped? could we have propped? could you have propped? could they have propped?	could I have been propping? could you have been propping? could he have been propping? could we have been propping? could you have been propping? could they have been propping?

Interro-negative form

Simple form	V-ing form
could I not prop? could you not prop? could he not prop? could we not prop? could you not prop? could they not prop?	could I not be propping? could you not be propping? could he not be propping? could we not be propping? could you not be propping? could they not be propping?
Perfect	V-ing perfect
could I not have propped? could you not have propped? could he not have propped? could we not have propped? could you not have propped? could they not have propped?	could I not have been propping? could you not have been propping? could he not have been propping? could we not have been propping? could you not have been propping? could they not have been propping?