Answer:
H₂
Explanation:
H₂ is hydrogen in its elemental form.
H₂O, NaCl, and CaCO₃ are all examples of elements added together to create compounds.
It is an Endothermic because the ice cube is absorbing the heat making the ice cube melt. It can not be Endothermic because it is not releasing any heat it is melting.
Oxygen is something that activated Cellar Reapiration that convets nutrients into energy (ATP).
Nucleus:direct all the organelles
