It's the third statement!
Answer:
magnesium + oxygen Right arrow magnesium oxide
Explanation:
1 kJ = 238.85 cal and
1 cal = 0.004187 kJ
so it will be 78.9×238.85 = <em><u>1</u></em><em><u>8</u></em><em><u>,</u></em><em><u>8</u></em><em><u>4</u></em><em><u>4</u></em><em> </em>calories
78.9 Kilojoules (kJ) = 18,844 Calories (IT) (cal)