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.

[Q]: the 7 july 2005 london bombings (also called 7/7) were suicide bomb attacks aimed at london's public transport system during the morning rush hour.
[A]: 7 july 2005 london bombings


[Q]: the english cocker spaniel is a breed of dog.
[A]: english cocker spaniel


[Q]: a viola is a musical instrument which is similar to the violin and cello.
[A]:
viola