Why do we need norms?

We need Norms because they provide order in society. Human beings need norms to guide and direct their behavior, to provide order and predictability in social relationships and to make sense of and understanding of each other's actions.

the following key ideas correctly express the key sentence.

restate key idea: most people can learn to swim in ten short lessons.

restate key idea: the majority of water-accident victims require mouth-to-mouth breathing.

restate key idea: an empty, tightly closed gallon jug will support a tired swimmer.  

restate key idea: first aid is to prevent accidents as well as assist in rescue.

explanation: the key idea needs to have the same topic as the key sentence (drowning and safety).