现代电子计算机发展的各个阶段的区分标志是（）。 元器件的发展水平。 计算机的运输速度。 软件的发展水平。 操作系统的更新换代。
According to the Code of Federal Regulations，on vessels other than river ferryboats and river vessels，how are periodic lifeboat weight tests required to be conducted?（） The lifeboat is lowered to near the water，loaded with the allowed capacity，lowered into the water until afloat，then released from the falls。 The lifeboat is loaded with the allowed capacity，lowered into the water until afloat，then released from the falls。 The lifeboat is lowered into the water until afloat，loaded with the allowed capacity，then released from the falls。 The lifeboat is lowered to near the water，loaded with the allowed capacity，then released from the fall。
液化天然气（LNG）储罐应（）对日静态蒸发率检测一次。 每年。 每半年。 每2年。 每月。
根据我国《海商法》的规定，海事赔偿责任限制的主体有（）。 船舶所有人。 救助人。 责任保险人。
对媒体处理的是（）。 模拟信号。 音频信号。 视频信号。 数字信号。
按照国际通行的标准，60岁以上的老年人口或65岁以上的老年人口在总人口中的比例超过（）或（），即可看作是达到了人口老龄化。
