Questions 15 to 18 are based on the following talk.

Although people often use the phrase the dictionary. There are many different kinds of dictionaries. Some general and some specialized. General dictionaries are all-purpose dictionaries that contain a broad range of words and common usage(Question 15). The first general dictionary that you used was probably a school dictionary.(Question 16) These dictionaries contain relatively few words and emphasize common words that you are most likely to encounter in your school years. Later, most people acquire a college dictionary. There dictionaries have more than 150, 000 entries with detailed definitions that are sufficient for most college students as well as general users. They also separately list abbreviations, biographical and geographical names, foreign words and phrases and tables of measures. The Random House Websters College Dictionary and the American Heritage Dictionary are well-known college dictionaries. For scholars or researchers, an abridged dictionary provides as many as 500, 000 entries that have detailed definitions and extensive word histories. You will find these dictionaries primarily in libraries and they often spend several volumes. Specialized dictionaries such as the drinking water dictionary or dictionary of legal terms are also very useful for scholars or researchers. (Question 18)

Question 15: What is an all-purpose dictionary?

Question 16: Which dictionary are you most likely to use in your university days?

Question 17: Which of the following is true about the college dictionary?

Question 18: According to the talk, what dictionary is especially useful for scholars and researchers?

大意：本文主要介绍了字典的分类和用途。总体来说，字典可以分为普通字典和专业字典两种。本文内容较简单。