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.    

The scientists _______ on this project try to find the solutions to air pollution.

• A. A. working
• B. B. worked
• C. C. are working
• D. D. who working

Rút ngọn mệnh đề. Mệnh đề đầy đủ: The scientists who are working on this project try to find the solutions to air pollution.