the; the
C. the; a                                      D. a; a 
15. Paper money was in ________ use in China when Marco Polo visited the country in ________ thirteenth century.
A. the; 不填                                B. the; the
C. 不填; the                                D. 不填; 不填
16. Most animals have little connection with ________ animals of ________ different kind unless they kill them for food.
A. the; a                                      B. 不填; a
C. the; the                                   D. 不填; the
17. Jumping out of ________ airplane at ten thousand feet is quite ________ exciting experience.
A. 不填, the                                  B. 不填, an
C. an, an                                       D. the, the
18. The sign reads “In case of ________ fire, break the glass and press ________ red button. ”
A. / ; a                                         B. / ; the
C. the; the                                    D. a; a
19. On ________ news today, there were ________ reports of heavy snow in that area.
A. the; the                                     B. the; 不填
C. 不填；不填                              D. 不填；the

【答案解析】
1. B. 因为collection (收藏品，收集物) 是可数名词，此处为单数，又不是特指，所以用不定冠词；books是名词复数表示种类，而非特指，所以不用冠词。又如：a fine collection of paintings精美的绘画收藏品。
2. B. word (话、话语) 是可数名词，without saying a word意为“没说一句话”；虽然silence (沉默)是不可数名词，但此处是特指前面提到的那种沉默，所以用the。