venting

gentlemen, a question for your expertise.

i have two vents up to the ceiling/attic floor represented by the two red lines in the picture. i have drawn three proposed spots to take it through the roof: A the green lines; B the blue lines and C the orange lines.

is there a preferred spot to bring this up through the roof? my immediate thought was to do it the green way but i started thinking maybe for some reason its unadvisable to put so close to the bottom ( it would be about 2' from the gutter). anyhow, thoughts are appreciated.

pic...

If it were me, I would go with proposal A. Most guys would join the two stacks in the attic and then reduce to a smaller sized vent before penetrating the roof; but if it were me, but I would keep it at 3".

I would go with A