Banana-Nut Muffins
["2 c. all-purpose flour", "1/4 c. sugar", "1 Tbsp. baking powder", "1/2 tsp. salt", "1 c. milk", "1 egg, beaten", "1/3 c. vegetable oil", "3/4 c. mashed banana", "1/2 c. chopped walnuts"]
["Preheat oven to 400\u00b0.", "Grease a 12-cup muffin pan."]
["flour", "sugar", "baking powder", "salt", "milk", "egg", "vegetable oil", "mashed banana", "walnuts"]