V:
Mark the letter A, B, C, or D on your answer sheet to show the underlined part that needs correction in each of the following questions.
Trả lời câu hỏi dưới đây:
What we know about certain diseases are still not sufficient to prevent to prevent them from spreading easily among the population.
Đáp án là B. are => is. What + clause: mệnh đề danh ngữ, động từ theo sau chia ở dang số ít.