Bộ 20 đề ôn thi vào Chuyên Anh năm 2023 có đáp án (Đề 15)

now it has scientific validity since recent research into tears has shown that they (4)

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now it has scientific validity since recent research into tears has shown that they (4) _____ a natural painkiller called enkaphalin.

contain

retain

hold

keep

Giải thích

Chọn A