Because the interest rate on mortgage loans is falling, many consumers are waiting to see how low the interest rate will be, so the number of new homes sold in January has fallen sharply, and while the sales have fallen sharply, the average price of new homes sold has surged. Which of the following, if correct, best explains the surge in the average price of a new house? ? ['Sales of higher-priced houses are not affected by the decline in sales, as their buyers are less limited by the total amount paid.', 'Labor agreement between builders and building unions expires next January.', 'Prices of new homes have been rising slowly over the past three years as the severity of the lack of housing has increased.', 'More homeowners sold their mid-priced homes again in January than in the previous three months.']