(a) Carbohydrates are one of the main types of nutrients found in food. They are the most important source of energy for the body of many organisms, including humans. Carbohydrate provides about 4 kcal per gram and is the energy that is used first to fuel muscles and the brain. Fat is also one of the three main macronutrients, along with carbohydrates and protein. Compared to carbohydrates and protein, each gram of fat provides more than twice the amount of calories (9 kcal per gram). So, the answer is carbohydates and fats.(b) Protein is the major structural component of cells and is responsible for the building and repair of body tissues. Proteins are organic molecules made up of amino acids – the building blocks of life. These amino acids are joined together by chemical bonds. They do most of the work in cells and are required for the structure, function, and regulation of the body's tissues and organs.So, the answer is proteins.(c) Vitamin A is a fat soluble vitamin that is also a powerful antioxidant. Vitamin A plays a critical role in maintaining healthy vision, neurological function, healthy skin, healthy immune system, and cell growth.So, the answer is vitamin A.(d) Minerals are components of foods that are involved in many body functions. For example, Calcium helps to maintain and build strong bones and teeth So, the answer is calcium.