[填空题] Questions 47 to 56 are based on the following passage.
The partnership between humans and animals dates back to the first domestication of animals in the Stone Age, as long as 9,000 years ago. But never have animals provided such (47) and particular help to humans as they do today in the form of trained (48) to people with disabilities. These animals, usually dogs, help people (49) tasks that would otherwise be difficult or even impossible. Service animals are not (50) but working animals doing a job; thus, (51) such as the Americans with Disabilities Act(1990) in the United States and the Disability Discrimination Act (1995) in the United Kingdom make service animals exempt from rules that (52) animals from public places and business.
The most familiar service animals are guide dogs whose job is to help people with (53) weakness or disability move about safely. Systematic training of