Final answer:
Lipids, commonly known as fats, contain the most calories per gram at nine calories, compared to the four calories per gram found in both carbohydrates and proteins. (Option b)
Step-by-step explanation:
The nutrient that contains the most calories per gram is lipids (fats). Comparatively, one gram of carbohydrates or protein has four calories, whereas one gram of lipids has nine calories. Vitamins and minerals, contrary to the provided information, are not macronutrients and do not provide energy in the form of calories.
Fats are essential for many body functions, including cell membrane construction and vitamin storage. However, fats are calorie-dense and excessive intake without burning the corresponding energy can lead to weight gain.