Which one is a national U.S. holiday?

All three holidays listed—Labor Day, Thanksgiving, and Independence Day—are designated as national holidays in the United States. These holidays are recognized across the country, providing time for celebration, reflection, and observance of cultural and historical significance.

Labor Day is celebrated on the first Monday in September and honors the contributions of American workers. Thanksgiving is observed on the fourth Thursday in November and is a time for families to come together and express gratitude, traditionally rooted in the harvest festivities of the early 1600s. Independence Day, celebrated on July 4th, marks the Declaration of Independence in 1776, symbolizing freedom and the birth of the nation.

Since all these holidays are officially recognized and celebrated nationwide, the correct choice is that they all qualify as national holidays.