Answer:
B.) Billboards
Explanation:
Companies have been using advertising to promote their products for centuries now, it has evolved and changed with society and technologies. In the 1920's automobiles were not common in most places, and while radios were on the raise most houses still did not have one, therefore the easiest way for a company to reach a wide audience was through billboards, because they could be placed in strategic locations where there was a higher transit of people and therefore, it could be seen by a lot of them.
