Which of the following sauces is vegetarian?

The Marsala Wine Sauce is considered vegetarian because it primarily consists of ingredients such as mushrooms, onions, and Marsala wine, which do not contain any meat products. This sauce is often used in various dishes within Italian cuisine, adding depth and flavor while keeping the dish suitable for vegetarians.

In contrast, Alfredo is a creamy sauce that may contain animal-derived ingredients like cheese and cream, making it unsuitable for those following a strict vegetarian diet that avoids all animal products. Chicken Piccata, on the other hand, specifically includes chicken, which clearly eliminates it from being vegetarian. Scampi Sauce typically contains shrimp or other seafood, also disqualifying it from the vegetarian category. Therefore, Marsala Wine Sauce stands out as the option that aligns with vegetarian requirements.