51. A. easier B. flatter C. harder D. lower
50. A. bird B. dog C. road D. car
49. A. see B. concentrate C. check D. care
48. A. air B. water C. ground D. woods
47. A. Can’t B. Don’t C. Aren’t D. Won’t
46. A. Luckily B. Probably C, Warmly D. Sadly
45. A. began B. stopped C. continued D. forgot
44. A. where B. while C. which D. why
43. A. Get out B. Move on C. Slow down D. Speed up
42. A. interesting B. moving C. puzzling D. annoying