英文: It's mandatory to pay taxes.
中文: 缴税是义务性的。英文: Experience with digital imaging is mandatory.
中文: 对数传图像的经验是强制性的。英文: Mandatory retirement ages need to go.
中文: 强制退休年龄必须废除。英文: Do mandatory testing exert any effet?
中文: 强制性化验有无作用?英文: BR>Every takeoff is optional. Every landing is mandatory.
中文: 每个起飞是自愿性的,每个降落是强迫性的。