The reason that businesses could attribute to a rise in sales to a radio advertising campaign is that the radio ads were the only promotion at the time.
When sales rise it is usually the result of a increased promotional campaign aimed at getting customers to buy goods and services.
If there is a rise in sales and radio ads are the only way to promote a company in a certain area, then it means that the radio ads are the reason the sales increased.
Find out more on advertising campaigns at https://brainly.com/question/357428.