27. The word "prevails" in line 23 is closest in meaning to (A) dominates (B) provides (C) develops (D) invests

33. Why does the author state in line 10 that observations are taken "just once every twelve hours?" (A) To indicate that the observations are timely (B) To show why the observations are on limited value (C) To compare data from balloons and computers (D) To give an example of international cooperation