单项选择题 （） means the level for which appropriate additional protective security measures shall be maintained for a period of time as a result of heightened risk of a security incident.

单项选择题 （） means the level for which minimum appropriate protective security measures shall be maintained at all times, threats and exchanging such information with appropriate Contracting Governments.

单项选择题 The additional mark （） in the Classification Certificate for Machinery means propulsion apparatus is remotely controlled on the navigating bridge control station, and engine assembly control station is unmanned periodically.