Correct Answer: A

Rationale: The correct answer is Estrogen (Choice A). Estrogen is produced by the ovaries and is essential for the maturation of eggs. It plays a crucial role in the development of secondary sexual characteristics, regulation of the menstrual cycle, and preparation of the uterus for implantation of a fertilized egg. Luteinizing Hormone (Choice B) is released by the pituitary gland and plays a role in ovulation, not the maturation of eggs. Progesterone (Choice C) is produced by the ovaries after ovulation and is important for preparing the uterus for pregnancy, not maturing eggs. Testosterone (Choice D) is a male sex hormone primarily produced in the testes, and while small amounts are also produced in the ovaries, it is not the hormone responsible for maturing eggs.

Correct Answer: B

Rationale: The correct answer is B. The diaphragm plays a crucial role in respiration by contracting and expanding the lungs. When the diaphragm contracts, it moves downward, creating more space in the chest cavity and allowing the lungs to expand. This expansion leads to a decrease in pressure inside the lungs, causing air to rush in. When the diaphragm relaxes, it moves back up, decreasing the space in the chest cavity and causing the lungs to deflate. This action increases the pressure in the lungs, leading to air being pushed out. Therefore, the diaphragm's main function is to facilitate the inhalation and exhalation of air by contracting and expanding the lungs. Choices A, C, and D are incorrect because the diaphragm's primary function is not to regulate air pressure in the lungs, store oxygen, or break down carbon dioxide. Instead, its main purpose is to aid in the mechanical process of breathing.

Correct Answer: B

Rationale: The primary function of the kidneys is to filter blood and remove waste products from the body, producing urine in the process. This function helps in maintaining the body's internal environment stable, a process known as homeostasis. Option A, 'To digest food,' is incorrect as digestion primarily occurs in the gastrointestinal system, not in the kidneys. Option C, 'To absorb nutrients,' is also incorrect because nutrient absorption mainly takes place in the intestines. Option D, 'To transport oxygen,' is incorrect as the lungs and circulatory system are responsible for oxygen transport, not the kidneys.

Correct Answer: B

Rationale: The correct answer is B: Vein. Veins carry blood back to the heart from various parts of the body, functioning as the vessels that return blood to the heart. Arteries, on the other hand, carry blood away from the heart to different parts of the body to deliver oxygen and nutrients. Capillaries are tiny blood vessels where the exchange of gases, nutrients, and waste products occurs between the blood and tissues. Lymphatic vessels are part of the lymphatic system, responsible for maintaining fluid balance and aiding in immunity. Therefore, the correct choice is B as it directly relates to the blood flow back to the heart.

Correct Answer: B

Rationale: The question inquires about the brain region responsible for voluntary muscle movements. The correct answer is the Cerebrum. The cerebrum is the main part of the brain involved in voluntary muscle control and motor coordination. The Medulla oblongata is primarily responsible for regulating vital functions like breathing and heart rate, not voluntary muscle movements. The Hypothalamus plays a role in regulating body temperature, thirst, hunger, and other homeostatic processes. The Thalamus serves as a relay station for sensory information but is not directly responsible for voluntary muscle movements.