Regarding the Validity of the Law of Conservation of Energy

Regarding the validity of the law of conservation of energy,

A) this law is a consequence of Newtonian physics, and so this law is valid in every known situation because Newtonian physics is valid in every known situation.
B) it is valid for any situation in which Newtonian physics is valid, but is often incorrect outside of that range.
C) it is valid in all situations except those situations involving heat.
D) it is valid in every known situation-- including those situations in which Newtonian physics is not valid.