The correct answer is indeed A) kept interest rates low.
Ok, let me try to resume.
When the central bank injects reserves, it encourages banks to lend out money at lower interest, attracting borrowers for this money and leading entrepreneurs to invest, once the higher interest rates would not be profitable. Interest rates coordinate savers and investors action. Investment requires resources to be frozen rather than consumed, meaning that less spending by the population reflects more resources available to fund these investments, resulting in a lower rate of interest.
When interest rates are pushed down by creating new money, the lower interest rate is not a representation of genuine savings by the public, it is artificially low. Increased business activity consumes resources while the population also keeps consuming more, causing a "tug-of-war" for resources between longer and shorter processes. When prices and interest eventually starts to rise, entrepreneurs find out their investment aren't actually profitable with these rates and are unable to complete the projects they started. This is the economic bubble, when the real economy can't withstand the perceived economy.
Now, finally going back into the answer.
During the late 1920s rates were kept artificially low by the Federal Reserve, sparking a boom, specially in the stock market, with prices rising up to 50 percent quickly. In 1929, once the government started tightening credit to cool down the overheated stock market it produced, the burst happened, leading the country into the Great Depression.
Sorry for the long explanation, hope you understand the concept ;)
