复数名词的所有格比如，parents' 是表示父母的还是表父母的东西，这是做形容词还是名词物主代词

如
There is a big bedroom in our flat.It is my parents'. (这里的 parents' 是相当于名词性物主代词)

They are my parents' photos. (这里的 parents' 相当于形容词性物主代词)