单项选择题 根据SOLAS公约第2-1章第53条的要求，对于周期性无人值班机器处所，主电源应满足如下附加要求，其中哪些是正确的？（）

多项选择题 载重线标志可用下述哪些方法永久地勘划在船舷中部两侧？（）

单项选择题 With reference to the requirements under IMO MODU CODE，Operating manuals containing guidance for the safe operation of the MODU unit for both normal and envisaged emergency conditions， to the satisfaction of the Administration should be provided on board and be readily available to all concerned. The manuals should， in addition to providing the necessary general information about the unit， contain guidance on and procedures for the operations that are vital to the safety of personnel and the unit.The operating manual for normal operations should include the following general descriptive information（）