I would say #2, because it is very important to eat a well balanced diet while also working out and staying physically active to stay healthy! However, the question asks, "Which of the following is a guideline for practicing good nutrition." That being said I would say #4 "Consume foods with a variety of nutrients and adequate portions.
Hope this helps!
D is the answer because i took the same test and got it right
C. can take the place of long-term goals
Hope this helps, mate!