Final answer:
Long, flat pastas pair optimally with light sauces such as pesto. Pesto is made from basil, garlic, pine nuts, cheese, and olive oil, providing flavor without heaviness, complementing the pasta's texture.
Step-by-step explanation:
Long, flat pastas are best suited to light sauces, and among the options given, the correct answer is d) Pesto. Pesto sauce is typically made from basil, garlic, pine nuts, Parmesan or Pecorino cheese, and olive oil. This combination creates a sauce that is flavorful but not heavy, making it an ideal complement to the texture of long, flat pasta like fettuccine or tagliatelle, which can carry the sauce without being overwhelmed by it.