Which of the following problems played the most important role in the collapse of Penn Square Bank and the creation of a boom and bust economy in the 1970s?

The best answer is C. changing oil prices.

The collapse of Penn Square Bank was significantly influenced by the volatility in oil prices during the 1970s, particularly following the oil crises. The fluctuations in oil prices impacted the economy and contributed to broader financial instability, which ultimately played a crucial role in the bank's failure and the associated boom and bust economic cycle of that era.