Mark the letter A,B,C, or D on your answer sheet to show the underline 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 them from spreading easily among the population.
D => is
- Chủ ngữ trong câu là cả cụm "What we know about certain diseases"