当他听到突如其来的坏消息时，脸上明显露出了不安的神情。

His face showed obvious ___perturbation when he heard the sudden bad news.

科学家们注意到磁场中的微小扰动可能影响实验结果。

Scientists noticed that small ___perturbations in the magnetic field could affect the experiment results.

卫星轨道的小扰动需要定期修正以确保正常运行。

Small ___perturbations in the satellite's orbit need regular adjustments to ensure proper operation.