Apple pie with crumb topping - chinese grandma

Ingredients

• 1 (9 inch) pie shell
• 6 cups peeled and thinly sliced apples (6-7 medium apples)
• 1 tablespoon lemon juice (optional)
• 3/4 cup granulated sugar
• 2 tablespoons all-purpose flour
• 1 teaspoon ground cinnamon
• 1/4 teaspoon ground nutmeg
• 1/2 cup raisins (optional)
• 1/2 cup chopped walnuts (optional)
• 1/2 cup all-purpose flour
• 1/2 cup packed brown sugar
• 3 tablespoons butter