Passage: The national cuisine of Nepal is Dhindo and Gundruk.The staple Nepali meal is dal bhat. Dal is a lentil soup, and is served over bhat (boiled rice), with tarkari (curried vegetables) together with achar (pickles) or chutni (spicy condiment made from fresh ingredients). It consists of non-vegetarian as well as vegetarian items. Mustard oil is a common cooking medium and a host of spices, including cumin, coriander, black pepper, sesame seeds, turmeric, garlic, ginger, methi (fenugreek), bay leaves, cloves, cinnamon, chilies and mustard seeds are used in cooking. Momo is a type of steamed dumpling with meat or vegetable fillings, and is a popular fast food in many regions of Nepal.

Question: What type of oil is used as a base in Dal soup?
Mustard