EXERCISE 3I. CHỌN TỪ/ CỤM TỪ THÍCH HỢP (ỨNG VỚI A, B, C, D) ĐỂ HÒAN TH...

49. According to the passage, the saw-mills have to be mobile because they are______. A. used to transport wood B. floated up the rivers C. moved away from clear areas D. transported near the market