This diabetes drug acts by decreasing the amount of glucose produced by the liver

The correct option is Biguanides.

To understand why this is the correct answer, let's break down the mechanism of action of the different classes of oral hypoglycemic agents listed in the options:
1. Biguanides (e.g., Metformin): The primary mechanism of action of biguanides is to decrease hepatic glucose production (gluconeogenesis). They also increase insulin sensitivity in peripheral tissues (like muscle) and decrease intestinal absorption of glucose.
2. Alpha-glucosidase inhibitors (e.g., Acarbose): These drugs act locally in the small intestine to inhibit the enzymes that break down complex carbohydrates into glucose, thereby delaying glucose absorption and lowering postprandial blood glucose levels.
3. Sulfonylureas (e.g., Glipizide, Glyburide): These agents stimulate insulin secretion from the beta cells of the pancreas by binding to specific sulfonylurea receptors, causing closure of ATP-sensitive potassium channels.
4. Meglitinides (e.g., Repaglinide): Similar to sulfonylureas, meglitinides stimulate insulin release from the pancreatic beta cells, though they bind to a different site and have a shorter duration of action.

Therefore, the class of drugs that specifically acts by decreasing glucose production by the liver is the Biguanides.