Write a multi-choice question for the following article: Article: Fake a book, leave a book. Public bookshelves are appearing across Germany on street corners, city squares and suburban supermarkets. In these free-for-all libraries, people can grab whatever they want to read, and leave behind anything they want for others. There's no need to register, no due date, and you can take or give as many as you want. "This project is aimed at everyone who likes to read regardless of age or education. It is open for everybody," Michael Aubermann, one of the organizers of the free book exchange in the city of Cologne, told The Associated Press. "We installed our other outdoor shelves last year and it's been working really well," said Aubermann, a 44-year-old who works in IT management. The public hook shelves, which are usually financed by donations and cared for by local \ volunteer groups, have appeared independently of each other in many cities across Germany including Berlin, Hannover and Bonn, and also in suburbs and villages. Each shelf holds around 200 books and it lakes about six weeks for a complete turnover, with all the old titles replaced by new ones, he said. While most of the shelves have so far been put up in upscale neighborhoods, Aubermann and the 20 volunteers who help look after the project are planning to put up future shelves in poor neighborhoods, where residents often don't have as much access to literature. So far, the Cologne book group has had few problems .Though a used-book seller once emptied every volume on a shelf to sell at a market. Another time the shelves were filled with material from a religious group. Even commercial book stores and online book retailers seem to support the idea of free book exchanges.
The answer to this question is:
Question: Which of the following is TRUE according to the text?Options:A Public bookshelves are only put in big cities.B One has to register if he wants to take a book.C One doesn't have to return the book at a fixed time.D The Cologne book group has had no problems until now.Answer:C