Bộ 10 đề ôn thi học sinh giỏi Tiếng anh 9 năm 2023 có đáp án (Đề 7)

and now it has scientific validity since recent research into tears has shown that they (59) _____ a natural painkiller called enkaphalin.

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and now it has scientific validity since recent research into tears has shown that they (59) _____ a natural painkiller called enkaphalin.

contain

retain

hold

keep

Giải thích

Chọn A