Astatement that explains what something does under the same conditions and is broadly agreed upon by the science community is
a.
a. law
b. theory
c. hypothesis
d. fact

Law

Example:
PV = k 
Where P is pressure of the gas and V is volume of the gas and k is constant. 
It easily derived by the equation above.
Boyle’s law states that when the gas amount and its temperature the same or held constant, within a closed system, the relation of the pressure exerted by the gas is inversely proportional to its volume. So in the situation, the pressure increases, so its volume decreases.