in turn by turns区别

in turn:

依次,轮流
反之，反过来

例句与用法:
1. The students clean the classroom everyday in turn.
学生们每天轮流打扫教室。

虽然这两个很接近，但是我直觉应选B
2. She asked the same question of everyone in turn.
她依次向每一个人问同样的问题。

3. Move the camera to each of these position in turn, press save on the remote, then a number from1 to4.
依次把摄像机移至各个位置，按遥控器上的Save键，然后按数字1－4。

4. Dilettante: a philanderer who seduces the several arts and letters each in turn for another.
业余艺术爱好者——是轮流引诱文学与艺术的不专一者。

5. The girls called out their names in turn.
那些女孩儿逐一报出自己的名字.

by turns:

轮流,交替地

例句与用法:
1. The shop assistants had to have their days off by turns.
店员要轮流休息。

2. We did the work by turns.
我们是轮流做这项工作的.

3. He gets cheerful and depressed by turns.
他的情绪高一阵低一阵。

B
因为奥运会不是各个国家依次举行，不能选A
而是交替

个人认为应该选B