English verb conjugation
COULD DESIGN

Regular verb: design - designed - designed

Affirmation

Simple form	V-ing form
I could design you could design he could design we could design you could design they could design	I could be designing you could be designing he could be designing we could be designing you could be designing they could be designing
Perfect	V-ing perfect
I could have designed you could have designed he could have designed we could have designed you could have designed they could have designed	I could have been designing you could have been designing he could have been designing we could have been designing you could have been designing they could have been designing

Negation

Simple form	V-ing form
I could not design you could not design he could not design we could not design you could not design they could not design	I could not be designing you could not be designing he could not be designing we could not be designing you could not be designing they could not be designing
Perfect	V-ing perfect
I could not have designed you could not have designed he could not have designed we could not have designed you could not have designed they could not have designed	I could not have been designing you could not have been designing he could not have been designing we could not have been designing you could not have been designing they could not have been designing

Interrogative form

Simple form	V-ing form
could I design? could you design? could he design? could we design? could you design? could they design?	could I be designing? could you be designing? could he be designing? could we be designing? could you be designing? could they be designing?
Perfect	V-ing perfect
could I have designed? could you have designed? could he have designed? could we have designed? could you have designed? could they have designed?	could I have been designing? could you have been designing? could he have been designing? could we have been designing? could you have been designing? could they have been designing?

Interro-negative form

Simple form	V-ing form
could I not design? could you not design? could he not design? could we not design? could you not design? could they not design?	could I not be designing? could you not be designing? could he not be designing? could we not be designing? could you not be designing? could they not be designing?
Perfect	V-ing perfect
could I not have designed? could you not have designed? could he not have designed? could we not have designed? could you not have designed? could they not have designed?	could I not have been designing? could you not have been designing? could he not have been designing? could we not have been designing? could you not have been designing? could they not have been designing?