18. The number 911 is a special number, ________, I think, that will be remembered by the Americans forever.
A. what B. it C. which D. one
19. By the year 1889, there were just 541 bison ________ in the whole of North America.
A. leaving alive B. to leave alive
C. to be left alive D. left alive
20. ---Jane, you’ve made such great efforts that you are ________ to pass the exam.
---It is very kind of you to say so, Mr. Smith.
A. easy B. bound C. possible D. convenient
