=>
41. nervous -> nervously
-> wait là động từ -> cần trạng từ
42. enough intelligent -> intelligent enough
-> be adj enough to V : đủ...để
43. when -> since
-> HTHT since QKĐ
44. getting -> to get
-> how to V : làm thế nào để
45. did happen ->happened
-> ask sb + từ để hỏi + S V
46. D thuận lợi và bất lợi của năng lượng mặt trời
47. A (Solar cells can easily be installed...advantages.)
48. C (Solar cells are totally...long lifetime./The main disadvatange of solar energy is that it costs about twice as much as traditional sources such as coal, oil, and gas.)
49. B (....traditional sources such as coal, oil, and gas.)
50. D benefit : lợi ích, điểm tốt