解析：细节理解题。根据第三段最后一句可知在英国患早老性痴呆病的人可能会增多，故答案为A项。

　　答案：A

　　2．The dogs are trained to perform tasks by ________．

　　A．making some sound signals

　　B．communicating with the patients

　　C．barking at the patients

　　D．reacting to some sound triggers

　　解析：细节理解题。根据第二段第一句可知答案为D项。

　　答案：D

　　3．What does the underlined word"them"in Paragraph 4 refer to?

　　A．Faces.　　　 B．Triggers.

　　C．Pets. D．Companions.

　　解析：词义猜测题。根据画线词所在句上面一句内容可推知them指的是pets。

　　答案：C

　　4．What is mainly talked about in the passage?

　　A．The idea of dementia dogs was developed by students.

　　B．Dogs are trained to assist Alzheimer's patients.

　　C．British people with Alzheimer's are in poor condition.

D．The dementia dogs perform most duties of a doctor.