PHILADELPHIA (AP) — President-elect Joe Biden and Vice President-elect Kamala Harris pitched in on Martin Luther King Jr. Day service projects ahead of inaugural events. Their work Monday came as a militarized and jittery Washington prepared for a swearing-in that will play out under extraordinary security. Biden and his wife, Jill, joined an assembly line in a Philadelphia parking lot, filling food boxes for people in need. Harris also took part in a service event in Washington. Some 25,000 National Guard troops have been dispatched across the city to bolster security. Monuments have been closed to the public until after Wednesday’s inaugural events.