Instructions: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Among the entities, try to find the best entity that is most likely to fill in "_" and classify the answers based on options.
Input: LONDON, England (CNN) -- There is a mathematical reason why the French Open is so different to any other of the Grand Slam tennis tournaments. Clay courts require a different type of game to grass and hard court surfaces The Roland Garros tournament is currently being contested, with Rafael Nadal looking for his fifth win in a row, and world number two Roger Federer searching for his first ever French Open title. • Get the latest French Open news What has brought problems to Federer, and to other greats like Pete Sampras and Boris Becker -- who never won a French Open, is the clay surface on which it is contested.Clay, grass and hard tennis court surfaces all produce different bouncesThe speed and bounce of certain courts can adversely affect a player's gameUse the CNN interactive to see how the bounce differs on each surface 
 Questions:One of the problems _ has on clay is that he has a single-handed backhand, and Nadal can get so much spin -- so Federer is trying to hit single-handed shots up around his shoulder." (A) LONDON (B) England (C) CNN (D) French Open (E) Grand Slam (F) Roland Garros (G) Rafael Nadal (H) Roger Federer (I) Pete Sampras (J) Boris Becker (K) Clay
Output:
(H)