【单选题】

There are many factors which may have an influence on adults and children being able to lead a healthy life.

Nowadays, people are very busy. Often, both parents work outside the home.Children are expected to take on more responsibility at home to help their parents. They also have sporting and leisure activities as well as school expectations.
The busyness also adds another factor: the need to use cars to get from one place to another quickly.
Today, society places a lot of emphasis on technology.Computers,DVDs,CDs, television, Playstations and Xboxes have become major leisure activities, rather than traditional more active pursuits. This has led to a more sedentary lifestyle.
The media provide entertainment and information. Unfortunately, they also promote fast food which fits easily into busy lifestyles. It is much more convenient at times to buy a quick takeaway rather than prepare a meal. The media constantly bombard (轰炸) their audience with "perfect" body images, the need to buy the most fashionable clothes, the most up-to-date computer games, the best places to visit and the best things to do.
Environments vary. We may be exposed to pollution, such as cigarette smoke. This can be harmful to people who suffer from breathing difficulties.Environments where passive smoking is unavoidable make it difficult to lead a healthy life.
Perhaps the important factor influencing healthy lifestyles is motivation, or the desire to be healthy.Any person who wants to be healthy will find a way to be healthy—if he/she is motivated enough!
According to the author, ______ may be the most important factor influencing healthy lifestyles.
A、technology B、cultural background
C、environment D、the desire to be healthy