unison

阅兵式上，士兵们步伐完全一致。

The soldiers march in perfect ___unison during the parade.

全班同学齐声回答老师的问题。

The whole class answered the teacher's question in ___unison.

小提琴和大提琴完美地齐奏同一个音符。

The violin and cello played the same note in perfect ___unison.