The correct answer is: "to raise depressed crop prices ".
The Agricultural Adjustment Act was issued in 1933 as a federal law which was part of the New Deal, the packet of measures implemented to boost the US economy after the 1929 crisis.
The prices of agricultural products were extremely low due to an excess supply or surplus situation in the market. The main aim of the AAA was to increase their prices, this is why the US government gave subsidies to farmers not to cultivate their fields and bought livestock to be slaugthered. The money to fund those operations was obtained from taxes collected from firms that processed those agricultural products.