Definition: Given a trivia question, classify broad topical category from this list: 'theater', 'geology', 'book', 'tv', 'astronomy', 'aviation', 'military', 'government', 'boxing', 'projects', 'metropolitan_transit', 'law', 'venture_capital', 'broadcast', 'biology', 'people', 'influence', 'baseball', 'spaceflight', 'media_common', 'cvg', 'opera', 'olympics', 'chemistry', 'visual_art', 'conferences', 'sports', 'language', 'travel', 'location', 'award', 'dining', 'martial_arts', 'comic_strips', 'computer', 'user', 'tennis', 'music', 'organization', 'food', 'event', 'transportation', 'fictional_universe', 'measurement_unit', 'meteorology', 'distilled_spirits', 'symbols', 'architecture', 'freebase', 'internet', 'fashion', 'boats', 'cricket', 'film', 'medicine', 'finance', 'comic_books', 'celebrities', 'soccer', 'games', 'time', 'geography', 'interests', 'common', 'base', 'business', 'periodicals', 'royalty', 'education', 'type', 'religion', 'automotive', 'exhibitions'.

Positive Example 1 -
Input: What country has borders with Libya, Sudan and Israel?
Output: location

Positive Example 2 -
Input: What child actress delighted audiences in Curly Top and Heidi?
Output: film

Negative Example 1 -
Input: Actor Jack Nicholson won his first Best Actor Oscar for which film?
Output: film

Negative Example 2 -
Input: Which famous novel was written in 1877 by Anna Sewell as a protest against cruelty to horses?
Output: anna sewell

Now complete the following example -
Input: Which four letter word beginning with U is the pigmented layer of the eye, lying beneath the sclera and cornea, and comprising of the iris, choroid and ciliary body?
Output: 

base