A student is investigating the affect of different salts on melting points. Four patches of ice of equal size are roped off and a different type of salt is poured on each, one receives table salt (NaCl), one receives Calcium Chloride (CaCl2), one receives Potassium Carbonate (KCO3) and the fourth receives inert sand instead. Each patch receives an equal amount of salt or sand. What could the student investigate? A. Amount of sand absorbed. B. The amount of oxygen released as each ice patch melts. C. How quickly the ice patches melt. D. The air temperature near each ice patch.