What is oil commonly used for in cooking?

Oil is commonly used in cooking primarily as a liquid fat. It serves several essential roles in the cooking process. First, it provides a medium for heat transfer, allowing food to cook evenly. When used for frying or sautéing, oil helps to achieve desirable textures and flavors, as it can create a crispy exterior on foods while keeping the inside moist.

Additionally, oil can be used in salad dressings and marinades, where it helps to coat ingredients and enhance their flavor profiles. Its ability to dissolve fat-soluble vitamins and compounds makes it a key ingredient in many recipes, as it can carry and amplify flavors.

While the other choices mention various cooking aspects, such as adding sweetness or thickening soups, they do not align with the primary purpose of oil in cooking. Oil primarily functions as a cooking fat, making it essential for a wide range of culinary techniques, from frying and roasting to baking and emulsifying.