答案为 A.
A:in a circle 意思为 成圆圈,联系上文表示站成一个圆圈,实际的圆圈
B:a用于辅音前;an用于元音前.因此B错误
C:in the circle 意思为按照圆圈,虚拟存在的圆圈.例句Each child
in a circle repeats a message to the next child
in the circle in a
whisper.
D:Instead they
move in circle
around the earth.取而代之的是他们反而绕着地球运转.