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).

no , per capita income is not a true measure of the development because: -it only tells us about average income not how income is distributed among the people.it only give us an idea of the economic aspect.it is only at the qualitative basis.moreover, income is not only the way of development other factors are also as much as important as income.

answer; i believe that the correct answer to the above question is; (tariff)