A Decision by the Federal Environmental Protection Agency (EPA) on the Amount

A decision by the federal Environmental Protection Agency (EPA) on the amount of carbon that can be emitted from a car's exhaust system conflicts with a California state law. In this situation, under the supremacy clause,​

A) ​both the decision and the law are invalid.
B) ​both the decision and the law apply concurrently.
C) ​California's law takes precedence.
D) ​the EPA's decision takes precedence.