Which two holidays are recognized as national holidays in the United States?

Martin Luther King Jr. Day and Memorial Day are recognized as national holidays in the United States. Martin Luther King Jr. Day, observed on the third Monday in January, honors the civil rights leader's contributions to American society and promotes equality for all. Memorial Day, observed on the last Monday of May, is a day of remembrance for those who have died in military service to the country, honoring their sacrifice and ensuring their legacy is not forgotten.

The other options include holidays that either aren’t nationally recognized or do not share the same significance. New Year's Day is a national holiday, but Valentine's Day is not officially recognized. Similarly, Halloween is widely celebrated, but it is not designated as a national holiday, while Thanksgiving is a federal holiday. Labor Day is a national holiday, but Earth Day does not hold the same status. Therefore, Martin Luther King Jr. Day and Memorial Day are the correct choices as they are officially recognized national holidays in the U.S.