Correct Answer: B

Rationale: The correct answer is B: To store and concentrate bile. The gallbladder's primary function is to store and concentrate bile, which is produced by the liver. Bile is released into the small intestine to aid in the digestion and absorption of fats. It helps in emulsifying fats and facilitating their breakdown by enzymes for better absorption. Choices A, C, and D are incorrect because the gallbladder does not produce bile (it is produced by the liver), detoxify harmful substances, or directly break down fats. Its main role is to store and concentrate bile before releasing it into the small intestine.

Correct Answer: A

Rationale: The primary function of the cardiovascular system is to pump blood throughout the body, ensuring that oxygen and nutrients are delivered to tissues while removing waste products. This circulation is essential for maintaining overall health and proper functioning of the body's cells and organs. Choices B, C, and D are incorrect because while the cardiovascular system does deliver nutrients to tissues indirectly by transporting them in the blood, regulating body temperature is primarily the role of the endocrine and nervous systems, and protecting the body from infection is the main function of the immune system.

Correct Answer: A

Rationale: The primary function of the liver is to detoxify harmful substances in the blood. While the liver also produces bile, which aids in digestion, stores glycogen for energy storage, and participates in metabolism, its main and essential function is detoxification. Producing insulin is mainly attributed to the pancreas, not the liver.

Correct Answer: A

Rationale: The spleen plays a crucial role in the lymphatic system by filtering blood, specifically removing old or damaged red blood cells. Additionally, the spleen produces lymphocytes, a type of white blood cell that plays a key role in the immune response by helping to fight off infections. Therefore, the correct answer is A, as the spleen is primarily involved in blood filtration and the production of lymphocytes rather than storing vitamins or regulating body temperature.

Correct Answer: C

Rationale: The correct answer is C: To clot blood. Platelets, also known as thrombocytes, have a primary function in blood clotting. They help in the process of coagulation, forming clots to prevent excessive bleeding when injuries occur. Platelets play a crucial role in maintaining the integrity of the circulatory system by sealing off damaged blood vessels and promoting wound healing. Choices A, B, and D are incorrect because platelets do not carry oxygen, fight infections, or transport nutrients in the blood.