Passage 1People have been talking about health for a long time b

Passage 1
People have been talking about health for a long time because people know the importance of it. People's understanding of health also becomes deeper with the progress in scientific research. Recently the term “health" has come to have a wider meaning than it used to. It no longer means just the absence of il0lness. Today, health means the well-being of your body, your mind and your relationship with other people. This new concept of health is closely related to another term——quality of life. Quality of life is the degree of overall satisfaction that a person gets from life.
Why has the emphasis of health shifted from the absence of disease to a broader focus on the quality of a person's life? One reason for this has to do with the length and conditions of life that people can now expect. Medical advances have made it possible for people today to live longer, healthier lives. Imagine for a moment that you were born in the year 1900. You could have expected on average to live until about the age of 47. In contrast, if you were born in the year 1999, you could expect to live to the age of 75.

This passage is mainly about ().
A、different understandings of the term “health"
B、improving the quality of life
C、the importance of quality living
D、people's expectations of a long and healthy life
【正确答案】：A