When the bell rang announcing the end of class students came out .A. by twos and threes B

问题补充：

When the bell rang announcing the end of class, students came out .

A. by twos and threes

B. by two and three

C. by two and three

D. by twos or threes

答案：

(答案→)A. by twos and threes

B. by two and three

C. by two and three

D. by twos or threes

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