Please answer the following question: Information:  - Anthony Horowitz, OBE (born 5 April 1955) is an English novelist and screenwriter specialising in mystery and suspense. His work for young adult readers includes "The Diamond Brothers" series, the "Alex Rider" series, and "The Power of Five" series (a.k.a. "The Gatekeepers"). His work for adults includes the novel and play "Mindgame" (2001), and two Sherlock Holmes novels "The House of Silk" (2011) and "Moriarty" (2014). He is the most recent author chosen to write a James Bond novel by the Ian Fleming estate, titled "Trigger Mortis" (2015).  - The Power of Five (also known as The Gatekeepers in the US) is a series of five fantasy and suspense novels, written by English author Anthony Horowitz and published between 2005 and 2012. It is an updated re-imagining of Horowitz's "Pentagram" series, which the author had left unfinished in the 1980s. The series is published in the United Kingdom by Walker Books Ltd and in the United States by Scholastic Press. The novels deal heavily in the occult and examples of things such as human sacrifice and blood rituals are major plot elements, such as in the first book, where the protagonist, Matthew Freeman, is hunted by a Cult who want to conduct a blood sacrifice on him to blast open a portal using a combination of nuclear physics and black magic, to unlock another dimension which is holding a group of ancient evil demons captive.  - Ian Lancaster Fleming (28 May 1908  12 August 1964) was an English author, journalist and naval intelligence officer who is best known for his James Bond series of spy novels. Fleming came from a wealthy family connected to the merchant bank Robert Fleming & Co., and his father was the Member of Parliament for Henley from 1910 until his death on the Western Front in 1917. Educated at Eton, Sandhurst and, briefly, the universities of Munich and Geneva, Fleming moved through several jobs before he started writing.  - Public Enemy Number Two is a novel written by Anthony Horowitz , the second in The Diamond Brothers series . The main character in the book is Nick Diamond , His older brother Herbert Simple -- who goes by the name Tim Diamond -- is an unsuccessful private detective . The novel is particularly known for its humour . It is followed by South By South East .  - Alex Rider is a series of spy novels by British author Anthony Horowitz about a 1415-year-old spy named Alex Rider. The series is aimed primarily at young adults. The series comprises ten novels, as well as five graphic novels, three short stories and a supplementary book. The first novel, "Stormbreaker", was released in the United Kingdom in 2000 and was adapted into a motion picture in 2006 starring Alex Pettyfer. A was released in 2006, based on the film which received negative reviews. The novels are published by Walker Books in the United Kingdom. They were first published by Puffin in the United States, but have been published more recently by Philomel Books, also an imprint of Penguin Books. The audio books are read by Simon Prebble. The tenth novel, "Russian Roulette", was released in September 2013. Horowitz has had great success with the series.  - The Diamond Brothers is a series of humorous children's detective books by Anthony Horowitz, the first of which was published in 1986. The books tell the adventures of the world's worst private detective, Tim Diamond, and his younger brother, Nick Diamond, who is considerably more intelligent. These books are aimed at young teenagers, slightly younger than those aimed at with the more recent "Alex Rider" series. However, both series star a teenage boy and include guns, fights and world-wide criminals. The most notable difference is that "The Diamond Brothers" series contains much more humour, with many puns, pop culture references and absurd situations. Although the books started in the late 1980s and have continued into the millennium, Nick and Tim remain roughly the same age (14 and 28 respectively), while London changes with the times (the newer books feature Oyster Cards and computers for example, whereas the older books feature parts of London that have long since changed, such as smoking in offices).  The entire series was re-issued in 2007 with new covers.    After reading the paragraphs above, we are interested in knowing the entity with which 'public enemy number two' exhibits the relationship of 'publisher'. Find the answer from the choices below.  Choices: - english  - philomel books  - portal  - puffin  - rider  - walker books
Answer:
walker books