Which of the following is likely to be a source of protein in a vegetarian pasta dish?

Tofu is a common plant-based source of protein, making it an excellent choice for vegetarian dishes, including pasta. It is derived from soybeans and is rich in protein while being versatile enough to absorb flavors from sauces and seasonings. This allows it to complement a variety of pasta dishes, providing both nutritional value and texture.

In contrast, the other options — chicken, fish, and pork — are all animal-based proteins and therefore not suitable for a vegetarian diet. A vegetarian pasta dish would avoid these meat options and instead focus on plant-derived proteins like tofu, as well as other ingredients such as beans or lentils that offer similar nutritional benefits.