English verb conjugation
COULD MARBLE

Regular verb: marble - marbled - marbled

Affirmation

Simple form	V-ing form
I could marble you could marble he could marble we could marble you could marble they could marble	I could be marbling you could be marbling he could be marbling we could be marbling you could be marbling they could be marbling
Perfect	V-ing perfect
I could have marbled you could have marbled he could have marbled we could have marbled you could have marbled they could have marbled	I could have been marbling you could have been marbling he could have been marbling we could have been marbling you could have been marbling they could have been marbling

Negation

Simple form	V-ing form
I could not marble you could not marble he could not marble we could not marble you could not marble they could not marble	I could not be marbling you could not be marbling he could not be marbling we could not be marbling you could not be marbling they could not be marbling
Perfect	V-ing perfect
I could not have marbled you could not have marbled he could not have marbled we could not have marbled you could not have marbled they could not have marbled	I could not have been marbling you could not have been marbling he could not have been marbling we could not have been marbling you could not have been marbling they could not have been marbling

Interrogative form

Simple form	V-ing form
could I marble? could you marble? could he marble? could we marble? could you marble? could they marble?	could I be marbling? could you be marbling? could he be marbling? could we be marbling? could you be marbling? could they be marbling?
Perfect	V-ing perfect
could I have marbled? could you have marbled? could he have marbled? could we have marbled? could you have marbled? could they have marbled?	could I have been marbling? could you have been marbling? could he have been marbling? could we have been marbling? could you have been marbling? could they have been marbling?

Interro-negative form

Simple form	V-ing form
could I not marble? could you not marble? could he not marble? could we not marble? could you not marble? could they not marble?	could I not be marbling? could you not be marbling? could he not be marbling? could we not be marbling? could you not be marbling? could they not be marbling?
Perfect	V-ing perfect
could I not have marbled? could you not have marbled? could he not have marbled? could we not have marbled? could you not have marbled? could they not have marbled?	could I not have been marbling? could you not have been marbling? could he not have been marbling? could we not have been marbling? could you not have been marbling? could they not have been marbling?