Given the question: I'm taking a test and have to guess the right answer to the question after the article. Article: Opposition is growing to the Berlin Zoo's plans to find a new home for Knut, the moneymaking celebrity polar bear whose popularity has been exploited by environmentalists and even Canadian tourism promoters. No longer cute, and just days before his second birthday, Knut will be given a new home that is expected to include a potential mating partner. The Berlin Zoo, facing the global economic crisis, can't afford the estimated $ 13 million it would take to acquire a female and a new home for them to share. "It's time for him to go--the sooner he gets a new home the better," said senior bear keeper Heiner Kloes. But some Berliners are beginning a campaign, collecting petition signatures and arguing that he's a tourist draw and a symbol as important as the Brandenburg Gate. "He means a lot to many people. When you're with him you forget your problems," Hartmut Wiedenroth, co-founder of the campaign, told Spiegel Online. Knut became an international celebrity in 2007, drawing huge crowds to his cage and _ sales of thousands of Knut toys and Knut-shaped candies. The Vancouver-based Canadian Tourism Commission made Knut a major part of its "Canada--Keep Exploring" campaign to draw tourists to the country-- and especially to polar bear country in northern Manitoba to see them in their natural habitat. Environmentalists also used the bear to promote the fight against global warming. But Knut's popularity diminished as his size increased to 210 kilograms, He was photographed at one point snapping at a child near his cage. In September his keeper, Thomas Doerflein, died of a heart attack. Doerflein, who became a celebrity himself after nursing the tiny ball of white fur when Knut's mother rejected him, had been re-assigned shortly after Knut's first birthday. Some animal rights critics said Knut has been showing unusually aggressive behavior because of his unnatural upbringing. Question: The Berlin Zoo intends to find a new home for Knut mainly because of _ . Options: A: the mother bear deserting him B: Knut's aggressive behavior C: lacking a skillful bear keeper D: its financial problem
The answer is:
D