What are the requirements to be a U.S. President?

The requirements to be a U.S. President, as outlined in the Constitution, include being at least 35 years old, being a natural-born citizen of the United States, and having lived in the country for at least 14 years. This ensures that the President has a mature understanding of the nation, a connection to its values and customs as a natural-born citizen, and sufficient time spent in the country to grasp its political landscape and societal issues.

The other options do not accurately reflect these constitutional requirements. For instance, being 40 years old is not necessary, and living in the U.S. for 10 years doesn't meet the established 14-year residency requirement. Additionally, having only been a U.S. citizen or a certain age is insufficient without the specific criteria of being a natural-born citizen and meeting the age and residency thresholds. Therefore, the outlined requirements make option B the correct answer.