Answer: D) 40%
Victory Gardens were started as a way of supporting the Allied war effort in Europe during World War II. The idea was to help to lower the price of vegetables needed by the US War Department to feed the troops. Between 1944 and 1945, nearly 20 million Americans had vegetable gardens in their yards or rooftops. Unfortunately, in 1946, with the war over, many residents did not plant Victory Gardens in expectation of greater produce availability.
Source: Wikipedia's Victory Garden Entry