What event does the FFA celebrate annually?

The correct choice is National FFA Week, which is celebrated annually as a time to recognize and promote agricultural education and the contributions of students involved in the Future Farmers of America organization. This event typically takes place during the week of George Washington's birthday, in honor of his legacy in agriculture and his support for the development of agricultural education in the United States.

National FFA Week includes various activities, events, and community service initiatives designed to raise awareness about the importance of agriculture and to highlight the role of FFA members in the community. It serves as an opportunity for FFA members to showcase their achievements, increase public awareness of the agricultural field, and encourage more students to consider careers in agriculture.

Other options like National Agriculture Day, Earth Day, and Harvest Festival are important in their own right but do not specifically celebrate the mission and activities of the FFA as directly as National FFA Week does. Each of those events has its own focus and significance but either does not connect distinctly to the FFA or is not celebrated annually by the organization itself.