Which of the following is true of junior posters?
a. They measure 14 by 48 feet, plus any extensions, and may carry either painted or printed messages.
b. They are typically concentrated in urban areas, where they can reach pedestrian as well as vehicular traffic.
c. They are three-dimensional or embellished by extensions that stretch beyond the frames of the structure.
d. They are giant electronic signs that incorporate movement, color, and flashy graphics to grab attention in high-traffic areas.
e. They use global positioning systems to give the exact location of the markets and the stores.