Animals and humans obtain the energy they need from what? A. food
B. water
C. carbon dioxide
D. photosynthesis

A. Food

Explanation:

Water alone does not give energy, Carbon Dioxide cannot be consumed healthily, and photosynthesis is for plants.

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.