Mark the letter A, B, C, or D on your answer sheet to indicate the cor

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.    

Urban planners carry out projects to develop a city. They look at the needs of local people and the environment when they do this.

• A. A. While carrying out projects to develop a city, urban planners look at the needs of local people and the environment when they do this.
• B. B. While carrying out projects to develop a city, urban planners look at the needs of local people and the environment.
• C. C. If they carry out projects to develop a city, urban planners look at the needs of local people and the environment when they do this.
• D. D. As carrying out projects to develop a city, urban planners look at the needs of local people and the environment.

vế "when they do this" chỉ ra rằng 2 hành động diễn ra đồng thời => loại C
As + mệnh đề => loại D vì sai ngữ pháp
While để thể hiện tính đồng thời giữa 2 hành động, không cần "when they do this" nữa
=> B