You shouldn't have been following him so closely;you should have kept your distance.翻译：你本不应该一直紧跟她，你本应和他保持距离。从后一句should have kept your distance，可以看出是对过去的虚拟，意思：你本应该保持距离。由此说明你没有保持距离，而是跟得紧，对过去进行行为的虚拟，用should have been doingSeen from space,the earth,with water covering 20% of its surface,looks like a "blue ball".seen 与句子主语the earth是被动关系，用过去分词作状语，相当于一个状语从句if it is seen from space,covering与其逻辑主语water是主动关系，用现在分词作定语，相当于定语从句，which covers不知是否清楚，若不明白，可继续追问。
