What land mammal holds the record for longest migration?

Caribou

In which film does Natalie Portman portray a ballerina named Nina Sayers who struggles with mental health? What alternative-rock band sang "1979" in the mid-1990s? "Just Friends" starred which actor as Chris Brander, who returns home at Christmas? What is the biological pigment responsible for human skin tanning in sunlight? Which person is known for discovering radioactivity?