Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions.
One necessary (A) preventive measure (B) to be taken (C) is that the public should be on the outlook (D) for symptoms of the disease.
One necessary (A) preventive measure (B) to be taken (C) is that the public should be on the outlook (D) for symptoms of the disease.
Đáp án đúng: D
The correct phrase is 'on the lookout'.