Choose (E) Element (C)Compound (M) Mixture for the following_____1. Cannot be decomposed by chemical means_____2. Has a definite composition_____3. Pure substance composed of identical atoms_____4. Can be separated by physical means_____5. Can be separated by chemical means_____6. Magnesium_____7. water_____8. air_____9. salt water solution_____10. can be heterogeneous_____11. ammonia (NH3)_____12. composition may vary_____13a____13b____13c_____13d