I think a, or d, but I can't say for certain. I am sorry.
Answer:
Two types of Commercial Agriculture: Daily Farming, Grain Farming.
Corn Belt. Fertile Region, located in the Mudwestern is a hub of corn and soybean production. Appalachia. Located in the Appalachian Mountains, it's a center of production for the cash crop Tobblaco.
D) selecting random sample allows for a more representative sample in a survey.