语法填空（共10小题；每小题1.5分，满分15分）
阅读下面短文，按照句子结构的语法和上下文连贯的要求，在空格处填入一个适当的词或使用括号中词语的正确形式填空，并将答案填写在答题卡标号为46～55的相应位置上。
Americans love pets. In America, there are more families with pets those with children. It is common ____ U.S. homes have some sort of pets, such as monkeys, snakes and even wolves. But Americans’ all-time favorites are cats and dogs, because dogs can offer protection from thieves and unwelcome visitors and cats can help get rid __the home unwanted pests. Beneath keeping pets, there lies a basic American belief: Pets have a right to be treated well. In Houston, Texas, dogs can have their dinner ____ (deliver) to their homes, just like pizza. Pets can even go with _owners on vacation. Besides, at least 75 animal welfare organizations exist in America which provide care and adoption services for ___ (home) and ill-treated animals. To pay for the high-tech health care, people can buy health insurance ___ their pets. Pets are ____ basic to American culture as hot dogs or apple pie. By now researchers ____ (discover) that interacting with animals lowers a person's blood pressure. Pets even encourage social relationships: They give their owners an appearance of friendliness, and they provide __ good topic of conversation.