Correct Answer: B

Rationale: The primary function of the heart is to pump oxygenated blood and nutrients throughout the body, supplying cells with vital substances. Choice A is incorrect as the kidneys are responsible for filtering blood. Choice C is incorrect as waste removal is primarily handled by organs like the kidneys and liver. Choice D is incorrect as regulating body temperature is mainly controlled by mechanisms such as sweating and shivering, not the heart.

Correct Answer: B

Rationale: The correct answer is B: 'To pump blood throughout the body.' The primary function of the heart in the circulatory system is to pump blood, which carries oxygen and nutrients, throughout the body. Choice A, 'To filter blood,' is incorrect as the heart does not filter blood; that is primarily done by the kidneys. Choice C, 'To absorb oxygen,' is incorrect as the lungs are responsible for oxygen absorption. Choice D, 'To remove carbon dioxide,' is incorrect as the lungs facilitate the removal of carbon dioxide from the body.

Correct Answer: B

Rationale: The main function of the large intestine is the absorption of water and electrolytes from indigestible food residues, helping to form solid waste (feces) for elimination. It mainly reabsorbs water and compacts the remaining material into feces, playing a crucial role in maintaining fluid balance in the body. Choices A, C, and D are incorrect because absorption of nutrients primarily occurs in the small intestine, secretion of digestive enzymes mainly occurs in the stomach and small intestine, and breaking down fats primarily occurs in the small intestine with the help of bile from the liver and enzymes.

Correct Answer: A

Rationale: The correct answer is A: To control breathing and heart rate. The medulla oblongata is a vital part of the brainstem responsible for regulating essential functions such as breathing, heart rate, and blood pressure. These functions are crucial for maintaining life, and the medulla oblongata plays a key role in ensuring the body's survival. Choices B, C, and D are incorrect because regulating body temperature is primarily controlled by the hypothalamus, coordinating voluntary movements is associated with the cerebellum and motor cortex, and processing sensory information is related to the thalamus and sensory cortex, not the medulla oblongata.

Correct Answer: B

Rationale: The correct answer is B: Triceps brachii. The triceps brachii muscle is responsible for extending the elbow joint. It is located on the back of the upper arm and acts in opposition to the biceps brachii, which is responsible for elbow flexion. The deltoid muscle is primarily responsible for shoulder abduction, not elbow extension. The pectoralis major muscle is involved in movements of the shoulder joint, not the elbow.