(A) Keratin

Hair is primarily composed of a protein called keratin. Keratin is a fibrous structural protein that forms the main component of hair, as well as nails and the outer layer of the skin. It provides strength and resilience to these structures. The other options—Casein, Globulin, and Mucin—are proteins found in other parts of the body and have different functions.

Entomology is the scientific study of insects. It involves the examination of the biology, behavior, ecology, taxonomy, physiology, and evolution of insects. Entomologists, the scientists who specialize in this field, study a vast and diverse group of organisms, which make up the largest class of animals on Earth. The knowledge gained through entomology has wide-ranging applications, from understanding ecosystems and biodiversity to pest management and forensic entomology.

Answer: A) Chloroplasts Explanation: Chloroplasts contains chlorophyll, the green substance in plants that allows them to create food from carbon dioxide and water called as photosynthesis.

Answer: C) Mitochondria Explanation: Cellular respiration is the multi-step process that creates energy from nutrients and food molecules. It begins in the cytoplasm of the cell, with the mitochondria functioning as the main organelle where the rest of the process continues and finishes. During respiration, glycolysis occurs in the cytoplasm of the cell.