Which of these changes to a modern lifestyle would promote the development of more-sustainable practices in the world food system?

a. eating more processed foods
b. buying fresh fruit all year long
c. switching from chicken to beef
d. eating only seasonal vegetables

The correct option is D.

Sustainable practices in the world food system refers to the concept of preserving natural resources by producing food crops in such a way that it will have minimal impact on the environment.

There are different ways by which one can make his diet more sustainable and these include buying as much seasonal food as one can.  Other strategies include: eating less animal products, eating less processed and packaged food, planting a garden, etc.