Step 1: Understanding the role of nutrients in the body.
In the body, different nutrients serve specific roles in maintaining health. Proteins, in particular, are essential for the growth, repair, and maintenance of tissues.
Step 2: Analyzing the options.
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(A) Carbohydrates: Incorrect. Carbohydrates provide energy to the body but are not primarily responsible for growth and repair.
(B) Triglycerides: Incorrect. Triglycerides are a type of fat that provide energy and help in storing energy but do not play a direct role in tissue repair.
(C) Vitamin B complex: Incorrect. While Vitamin B complex plays a key role in metabolism, it is not directly responsible for growth and repair.
(D) Protein: Correct. Proteins are the building blocks of the body and are crucial for growth, tissue repair, and immune function.
Step 3: Conclusion.
Therefore, the correct answer is (D) Protein, as it is essential for growth and tissue repair in the body.
Final Answer: Protein.