How does a production possibility chart assist in outlining opprotunity cost

Areal estate salesperson is often approached by home buyers of a particular race. his usual practice is to show them homes in neighborhoods where most of the residents are the same race as the buyers. he avoids showing these buyers properties in integrated areas. this is called:

Which two words in this excerpt from the count of monte cristo can be used as synonyms to determine the meaning of the word grotto? dantès entered the second grotto. the second grotto was lower and more gloomy than the first; the air that could only enter by the newly formed opening had the mephitic smell dantès was surprised not to find in the outer cavern. he waited in order to allow pure air to displace the foul atmosphere, and then went on.

Why is it necessary to obey social norms? write briefly.