A、Brave and determined. B、Cautious and friendly. C、Considerate and optimistic. D、Unusual and scholarly. D选项均为描述人性格特征的形容词表明，本题考查某

One of the greatest contributions to the first Oxford English Dictionary was also one of its most unusual. In 1879, Oxford University in England asked Prof. James Murray to serve as editor for what was to be the most ambitious dictionary in the history of the English language.
    This was a huge task. So Murrary had to find volunteers from Britain, the United States, and the British colonies to search every newspaper, magazine, and book ever written in English. Hundreds of volunteers responded, including William Chester Minor. Dr. Minor was an American Surgeon who had served in the Civil War and was now living in England. He gave his address as "Broadmoor, Crowthorne, Berkshire," 50 miles from Oxford.
    Minor joined the army of volunteers sending words and quotations to Murray. Over the next years, he became one of the staffs most valued contributors.
    But he was also a mystery. In spite of many invitations, he would always decline to visit Oxford. So in 1897, Murray finally decided to travel to Crowthorne himself. When he arrived, he found Minor locked in a book-lined cell at the Broadmoor Asylum for the Criminally Insane.
    Murray and Minor became friends, sharing their love of words. Minor continued contributing to the dictionary, sending in more than 10,000 submissions in 20 years. Murray continued to visit Minor regularly, sometimes taking walks with him around the asylum grounds.
    In 1910, Minor left Broadmoor for an asylum in his native America. Murray was at the port to wave goodbye to his remarkable friend.
    Minor died in 1920, seven years before the first edition of the Oxford English Dictionary was completed. The 12 volumes defined 414,825 words, and thousands of them were contributions from a very scholarly and devoted asylum patient.
Questions 16 to 19 are based on the passage you have just heard.
16. How did Dr. Minor contribute to the dictionary?
17. Why did Dr. Minor refuse to visit Oxford?
18. What was the main reason of Prof. Murray and Dr. Minor becoming friends?
19. Which of the following best describes Dr. Minor?