The LEAST likely choice is definitely “Reduced amount of agricultural land in production due to higher crop yields per acre”.
Indeed, corporations would keep the existing land allotting structure to maximize profit since demand is so high that even if all the existing doubled, demand would still be very high. Additionally, they lobby intensely Congress for anything they can get and subsidies are part of that. Finally it is arguable that the yield per acre would be that high as GMO crops have been found to actually impoverish soils in several cases (research is still ongoing and not conclusive yet).