the answer is c. this is because the question says what is the main idea based on the title which is how to eat more healthy. and in this case the answer choice C states what you have to do to eat more healthy.
what is a central idea:
The central idea is the central, unifying element of the story, which ties together all of the other elements of fiction used by the author to tell the story. The central idea can be best described as the dominant impression or the universal, generic truth found in the story.
