requires that if Congress and the states both seek to regulate an area of concurrent authority, the supremacy clause requires states to meet national standards if national standards are higher than state standards.

a. The guarantee clause
b. Preemption
c. The 10th Amendment

b. Preemption

Explanation:

In United States federal law, Preemption  refers to the authority of the federal law over state law in case of any conflicts arising during enacting a law regulating in the concurrent area if the state law is of lower standard as compared to the national federal law. In other words it is the invalidation of the United States state's law which conflicts with the United States Congress or federal laws.

Hence the correct option is (b).

sounds good to me mate!