Linda decides to visit her friends john and mary. as she knocks on the door, she hears her friends quarrelling. but when they open the door, john and mary are smiling. linda acts as though she has not heard the quarrel. this is an example of

This is an example of face-saving behavior.
She did this in order to avoid feeling embarrassed, or to lessen the embarrassing situation which may have happened if she showed that she heard them fighting. By pretending she didn't hear anything, she kept the appearance of a normal situation.