2. Salt
“1. Pumpkin pie” is incorrect. You can see two phases — the crust and the filling, and each of these is also a mixture.
“3. Iced tea” is incorrect. You can see two phases — the ice and the tea, and the tea is a solution of several substances in water.
“4. Salt water” is incorrect. Although it is homogeneous, it consists of two substances — salt and water.