Tham khảo tài liệu 'anh văn toefl structure-016', ngoại ngữ, toefl - ielts - toeic phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Anh văn TOEFL Structure-016 There is evidence that prehistoric humans used fire --400 000 B. C. u a so early u b the earliest u c as early as u d so early that 2 In the late 1800 s Ellen Richards began work in the new field of sanitary science which was concerned with waste removal water purification and . u a to ventilate adequately u b adequate ventilation u c adequate ventilate u d ventilation adequately 3 red clover high in protein content is an extremely important leguminous hay and pasture plant of the eastern United States. a The u b There us the u c It is the u d That the 4 The topology of Mars is more than that of any other .
