Here are the answers to your questions:
Question 1: Which of these was a factor that led to the Dust Bowl?
Answer: D - overproduction by farmers
Question 2: During which decade did the worst of the Dust Bowl conditions occur?
Answer: B - 1930s
Question 3: The Dust Bowl ruined over __________ acres of farmland during this time period.
Answer: B - 50 million acres