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 couldn't prop you couldn't prop he couldn't prop we couldn't prop you couldn't prop they couldn't prop	I couldn't be propping you couldn't be propping he couldn't be propping we couldn't be propping you couldn't be propping they couldn't be propping
Perfect	V-ing perfect
I couldn't have propped you couldn't have propped he couldn't have propped we couldn't have propped you couldn't have propped they couldn't have propped	I couldn't have been propping you couldn't have been propping he couldn't have been propping we couldn't have been propping you couldn't have been propping they couldn't 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
couldn't I prop? couldn't you prop? couldn't he prop? couldn't we prop? couldn't you prop? couldn't they prop?	couldn't I be propping? couldn't you be propping? couldn't he be propping? couldn't we be propping? couldn't you be propping? couldn't they be propping?
Perfect	V-ing perfect
couldn't I have propped? couldn't you have propped? couldn't he have propped? couldn't we have propped? couldn't you have propped? couldn't they have propped?	couldn't I have been propping? couldn't you have been propping? couldn't he have been propping? couldn't we have been propping? couldn't you have been propping? couldn't they have been propping?