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.
The production of different kinds of artificial materials are essential to the conservation of our natural resources
A. artificial
B. are essential
C. to
D. The production
Đáp án là B
chủ ngữ ‘the production‟ là số ít => sửa ‘are essential‟ thành ‘is essential‟.