The correct answer is D. All of these.
Air-entraining materials are added to concrete to improve its workability, durability, and resistance to freezing and thawing. They do this by creating tiny air bubbles in the concrete, which act as tiny voids that can absorb water and prevent it from freezing and expanding.
Gypsum is a common air-entraining material. It is a white, powdery mineral that is used to make plaster, drywall, and other building materials. Gypsum reacts with water to form calcium sulfate hemihydrate, which is a gel that traps air bubbles as it hardens.
Acid-resistant cement is a type of cement that is resistant to attack by acids. It is made by adding a small amount of aluminum powder to Portland cement, which reacts with the acid to form a protective layer on the surface of the concrete.
Quick lime is a type of lime that is produced by heating limestone to a high temperature. It is a white, powdery substance that is used to make mortar, plaster, and other building materials. Quick lime reacts with water to form calcium hydroxide, which is a gel that traps air bubbles as it hardens.
All of these materials can be used to improve the quality of concrete.