The tendency for the presence of other people to increase performance on easy tasks and impair performance on difficult tasks is known as and is when a person exerts less effort they work in a group than when working alone.

Social facilitation; social loafing                                                                                  

Explanation:

Social facilitation: In social psychology, the term "social facilitation" is described as a phenomenon that states that different individuals tend to perform well on a particular task when they are being surrounded with other peoples. It was first discovered by "Norman Triplett" during 1898 and labeled as social facilitation by a psychologist named Floyd Allport.

Social loafing: In social psychology, the term "social loafing" is also referred as "ringelmann effect" as it was first proposed by Max Ringelmann during 1913, and is described as a phenomenon in which an individual tends to exert less effort on a specific task if he or she is in a group as compared to the scenario in which he or she works alone.

In the question above, the given statement signifies the concept of social facilitation and social loafing.

ever since wwii tmthey always did hated each other.

even though you have attached neither the chart nor the generalizations, i have located them online. the right answer is d, since they are asking you about a generalization. you can only infer from the chart that between 2008 and 2009 the number of employed workers decreased significantly (from over 115 millions to 107 millions approximately), which signals some type of economic crisis.