A(n) is the entire collection of subjects about which we would like information.

The Population is the entire collection of subjects about which we would like information.Population information can be measured only by census.But we don't know the exact population of any countries,only for certain years we can know the information through a census. Other than census we can collect using online surveys.We can't find the exact population information because every day new born and death happens.

No, you just need to see your messages  within 24hrs, our the msg is gone. and you need to screenshot it if it's important.