Correct Answer: C

Rationale: The myelin sheath, a fatty substance that insulates nerve fibers, is derived from nervous tissue, specifically glial cells. Glial cells, including oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system, are responsible for producing the myelin sheath that surrounds and insulates nerve fibers, aiding in the conduction of nerve impulses. Epithelial tissue (Choice A), Muscle tissue (Choice B), and Connective tissue (Choice D) are not responsible for producing the myelin sheath; instead, nervous tissue (glial cells) plays this crucial role.

Correct Answer: A

Rationale: The correct answer is 'Atom.' An atom is the fundamental unit of an element that can exist independently and retain its unique chemical properties. It consists of a nucleus containing protons and neutrons, surrounded by electrons. Choice B, 'Molecule,' is incorrect because a molecule is a combination of two or more atoms bonded together. Choice C, 'Compound,' is incorrect as a compound is a substance formed by the chemical combination of two or more different elements. Choice D, 'Mixture,' is incorrect since a mixture is a blend of two or more substances physically combined, but the individual components retain their properties.

Correct Answer: A

Rationale: The correct arrangement of the small intestine segments, from the stomach to the large intestine, is Duodenum, Jejunum, and Ileum. The small intestine begins with the duodenum, then continues to the jejunum, and finally, it ends with the ileum before connecting to the large intestine. Option A, 'Duodenum, Jejunum, Ileum,' is the correct sequence. Choices B and C have the segments in incorrect order, not following the anatomical arrangement of the small intestine. Therefore, they are incorrect. Option D, 'None of the above,' is also incorrect as the correct sequence is provided in option A.

Correct Answer: D

Rationale: Solar cells, also known as photovoltaic cells, convert solar energy from sunlight directly into electrical energy through a process called the photovoltaic effect. This process involves the absorption of photons from sunlight, which then generate an electric current. Choice A is incorrect because solar cells do not convert electrical energy into light energy. Choice B is incorrect as solar cells do not involve chemical energy conversion. Choice C is incorrect because solar cells do not primarily convert solar energy into thermal energy. Therefore, the correct answer is D) Solar energy to electrical energy.

Correct Answer: B

Rationale: The correct answer is B: To transport oxygen. Red blood cells play a crucial role in carrying oxygen from the lungs to all the tissues and organs in the body. This oxygen transport is essential for cellular respiration, where oxygen is used in the production of energy. Red blood cells do not primarily transport nutrients, fight infection, or produce antibodies. Choice A is incorrect because while red blood cells do carry some nutrients, their primary function is to transport oxygen. Choice C is incorrect because immune cells, not red blood cells, are responsible for fighting infections. Choice D is incorrect as antibody production is mainly carried out by specialized white blood cells, not red blood cells.