（）调查是通过对调查总体的大致考察和了解，选择少数具有代表性的单位进行调查，从而达到认识查总体基本情况的目的。

Since we are social beings, the quality of our lives depends in large measure on our interpersonal relationships. One strength of the human conditions is our possibility to give and receive support from one another under stressful conditions. Social support makes up of the exchange of resources among people based on their interpersonal ties. Those of us with p support systems appear better able to deal with major life changes and daily problems. People with p social ties live longer and have better health than those without such ties. Studies over types of illnesses, from depression to heart disease, show that the presence of social support helps people defend themselves against illness, and the absence of such support makes poor health more likely.
Social support cushions stress in a number of ways. Firstly, friends, relatives and co-workers may let us know that they value us. Our self-respect is strengthened when we feel accepted by others in spite of our faults and difficulties. Secondly, other people often provide us with informational support. They help us to define and understand our problems and find solutions to them. Thirdly, we typically find social companionship supportive. Taking part in free-time activities with others helps us to meet our social needs while at the same time distracting us from our worries and troubles. Finally, other people may give us instrumental support—money aid, material resources, and needed services—that reduces stress by helping us resolve and deal with our problems.

The researches show that people’s physical and mental health ______.

A. lies in the social medical care systems which support them
B. has much to do with the amount of support they get from others
C. depends on their ability to deal with daily worries and troubles
D. is related to their courage for dealing with major life changes