Correct Answer: D

Rationale: When human cells divide by meiosis, the resulting cells contain 23 chromosomes. This is because meiosis is a cell division process that reduces the chromosome number by half, resulting in cells with a haploid number of chromosomes. In humans, the diploid number of chromosomes is 46. Therefore, after meiosis, the resulting cells have 23 chromosomes, ensuring the correct chromosome number is restored upon fertilization. Choices A, B, and C are incorrect as they do not represent the correct chromosome number resulting from meiosis in human cells.

Correct Answer: A

Rationale: The correct answer is the sinoatrial node. This node, also referred to as the pacemaker of the heart, is responsible for initiating the electrical impulses that stimulate cardiac muscle contractions. It plays a crucial role in setting the pace and rhythm of the heart's contractions. Choices B, C, and D (the left ventricle, the aorta, and the tricuspid valve, respectively) do not serve as the primary electrical stimulator of the cardiac muscle. While the left ventricle is a chamber of the heart that pumps oxygenated blood to the body, the aorta is the main artery that carries blood away from the heart, and the tricuspid valve is a one-way valve that ensures blood flows properly through the heart, none of these structures initiate the electrical impulses that cause the cardiac muscle to contract.

Correct Answer: B

Rationale: The correct answer is B: Endocrine system. The adrenal glands are part of the endocrine system, not the immune, lymphatic, or respiratory system. The endocrine system is responsible for producing and regulating hormones that control various bodily functions. The adrenal glands specifically produce hormones like cortisol and adrenaline, which are critical for the body's response to stress and metabolic processes. The immune system is responsible for defending the body against infections and diseases, the lymphatic system is involved in immunity and fluid balance, and the respiratory system is responsible for gas exchange in the body. Therefore, choices A, C, and D are incorrect in the context of the adrenal glands.

Correct Answer: D

Rationale: The correct answer is D, Adipose. Adipose tissue is a type of connective tissue that stores fat, not muscle tissue. Skeletal, smooth, and cardiac are all types of muscle tissues found in the body. Skeletal muscle tissue is responsible for voluntary movements and is attached to bones. Smooth muscle tissue is found in the walls of hollow organs and blood vessels, responsible for involuntary movements. Cardiac muscle tissue is found in the heart and is responsible for pumping blood throughout the body. Adipose tissue, on the other hand, primarily functions as a storage site for energy in the form of fat.

Correct Answer: D

Rationale: The correct answer is D. The immune system's primary function is to help the body avoid, detect, and eliminate infections. It does so by recognizing and responding to harmful pathogens, such as bacteria and viruses, to maintain the body's health and well-being. Choices A, B, and C are incorrect because the immune system is not controlled by the hypothalamus, its main role is not to filter toxins out of the blood, and while it can stimulate the production of certain immune cells, it does not directly stimulate the production of blood cells in response to infections.