Which of these factors helped to popularize smoking in the United States?

A) The availability of ready-made cigarettes
B) The development of a "blended" cigarette
C) The historically low prices for cigarettes
D) Both a and b helped popularize smoking

The availability of ready-made cigarettes and the development of a "blended" cigarette were two significant factors that helped popularize smoking in the United States. The former made it much easier and more convenient to smoke, while the latter improved the taste and quality of cigarettes, making them more enjoyable for consumers. Together, these factors paved the way for cigarettes to become a widely accepted and popular habit in American society.