单项选择题

The mast fundamental group to which a person belongs is the family. The institution of the family exists in almost every human culture. It is considered by behavioral scientists to be one of the oldest institutions in human history.
The family unit serves many important functions. The performance of these functions is the reason for the family’s importance. Above all, the family serves as a mechanism of species survival.
Families also have important economic functions. In primitive societies, the tasks of gathering food and providing shelter were divided among family members. Today, both husband and wife may work and share the duties of homemaking and child mating.
In addition to its survival and economic functions, the family gives its members social status. In many societies, a person is not considered a complete member until he has married and produces children. Finally, the family helps to meet the basic emotional needs of a person through the love and support received from parents, siblings(兄弟姐妹) and relatives.

Which of the following best states the main idea of the passage()

A.The family has changed greatly over time.
B.Many of the functions of the family today are being performed by government agencies.
C.The most important role for the family is to gather food.
D.The family has served many useful functions throughout history.