他们的手表经过了仔细调整，以确保时间的同步。

Their watches were carefully adjusted to maintain perfect ___synchronism.

舞者们需要保持动作的同步才能呈现出完美的表演。

The dancers need to maintain perfect ___synchronization in their movements for a flawless performance.

工程师检查了音频和字幕的同步性。

The engineer checked the ___synchronism between the audio and subtitles.