The greater presence of animals in health-care settings comes amid increasing evidence that pets are good for us and can play a significant role in patients' recovery. Sometimes known as "pet therapy," animal-assisted therapy and activities have become an important tool for doctors and rehabilitation specialists. "Animals motivate people to participate in their therapies, brighten patients' days, give them a chance to talk about the animals in their lives, and give them the opportunity to forget that they're in a hospital," says Dianne Bell, coordinator of the Delta Society Pet Partners program, which helps train and register animals and their owners for volunteer positions in health- care settings.
Currently there are more than 8,000 Delta Society Pet Partner teams in the United States and a handful of other countries, says Bell. Each makes an average of three visits per month and is likely to touch the lives of more than 540 people per year. And these figures don't include the hundreds of other volunteer teams registered through different programs.
According to the passage, pets are used in health-care settings mainly because _________.

A. doctors like pets and want to keep them where they work.
B. evidence shows that pets help patients recover.
C. patients can help train and register these pets.
D. some experiments need these pets.