Generate a topic word for the given sentence. A topic word is usually the name of a person, place, animal, concept or object the sentence is focusing on.

[EX Q]: the occipital lobe is the back part of a mammal's brain.
[EX A]: occipital lobe

[EX Q]: a group of his hostages nicknamed him "jihadi john" since he was part of a four-person terrorist cell with british accents whom they called "the beatles".
[EX A]: jihadi john

[EX Q]: the viverridae is a family of small to medium-sized mammals, the viverrids.
[EX A]:
viverridae