According to scientists (A) who study birds,(B) upon hatching,(C) ducklings have already known to swim.(D)

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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

scientists

birds

upon hatching

to swim

Giải thích

Đáp án D.

“to swim” -> “how to swim”: upon hatching, ducklings have already known how to swim (trước khi nở, vịt con đã biết được bơi như thế nào