Although we are concerned about the problem of energy sources, we must not fail

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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.

Although we are concerned about the problem of energy sources, we must not fail recognizing the need for environmental protection

must not

recognizing

for

concerned about

Giải thích

Đáp án là B

fail to do something (thất bại trong việc làm gì đó) là cấu trúc cố định. => sửa ‘recognizing‟ thành ‘to recognize‟.