Endothermic reaction : A reaction in which the system absorb energy, usually in the form of heat
the one that is an endothermic reaction is : D. Thawing ice
hope this helps
Here is your answer
C3H8 + O2-----> CO2 + H2O
Balancing C atoms
C3H8 + O2------> 3CO2 + H2O
Balancing H atoms
C3H8 + O2------> 3CO2 + 4H2O
Balancing O atoms
C3H8 +

O2------->

CO2 +

H2O
Hence the equation is balanced.
HOPE IT IS USEFUL
Depending on the reaction, we could monitor the progress towards equilibrium by observing the concentration of the reactant and the product are equal with time.
<h3>What is equilibrium?</h3>
Equilibrium is a stage of reaction in which the rate of forwarding reaction is equal to the rate of backward reaction and equilibrium is stable at the reversible state of mode.
The concentration of reactant and product must also be equal or the same as the time then only it can be an equilibrium reaction.
Therefore equilibrium depends on the reaction, the concentration of the reactant and the product are equal with time.
Learn more about equilibrium, here:
brainly.com/question/13463225
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Vaccine
Because scientists normally put the cure in a form to get injected into you and since a vaccine is basically a shot vaccine would most likely be correct