Correct Answer: A

Rationale: The correct answer is the corpus callosum. It is a thick band of nerve fibers that connects the two hemispheres of the brain, facilitating communication and coordination between them. The thalamus acts as a relay station for sensory information, the hypothalamus regulates basic functions like hunger and thirst, and the medulla oblongata controls vital functions such as breathing and heart rate. Therefore, choices B, C, and D are incorrect as they do not specifically connect the two hemispheres of the brain as the corpus callosum does.

Correct Answer: A

Rationale: The compound CH₃COOH is commonly known as acetic acid. Acetic acid is a clear, colorless liquid with a sour taste and a pungent smell. It is a weak acid found in vinegar and is used in the production of various chemicals. Formic acid, butyric acid, and propionic acid are different organic acids with distinct chemical structures and properties, but they are not the common name for the compound CH₃COOH.

Correct Answer: B

Rationale: When a car brakes to a stop, friction between the tires and the road acts as an unbalanced force causing deceleration. This friction force opposes the motion of the car, resulting in a decrease in speed until the car comes to a complete stop. Choice A is incorrect because if the forces were balanced, the car would not experience any deceleration. Choice C is incorrect because if the force were unbalanced in the direction of motion, the car would continue to move instead of coming to a stop. Choice D is incorrect because friction between the tires and the road does exert a force, causing deceleration.

Correct Answer: C

Rationale: The primary function of hair on the human body is protection. Hair acts as a barrier to protect the skin from external factors such as sunlight, dust, and other environmental elements. While hair can also provide some insulation by trapping heat near the body and contribute to sensory perception by detecting touch or movements, its main role is to safeguard the skin from potential harm, making protection the most essential function. Vitamin D synthesis is primarily related to the skin's exposure to sunlight and is not a direct function of hair.

Correct Answer: A

Rationale: The correct answer is simple squamous epithelium (Choice A). The inner surface of blood vessels is lined by a single layer of flattened cells, known as simple squamous epithelium. This epithelium type is thin and allows for efficient diffusion and filtration, which is essential for the exchange of gases and nutrients across blood vessel walls. Simple columnar epithelium (Choice B) is typically found in the lining of the gastrointestinal tract and is responsible for absorption and secretion. Stratified squamous epithelium (Choice C) is commonly found in the skin, providing protection against mechanical stress. Stratified columnar epithelium (Choice D) is not a characteristic epithelium type found in the lining of blood vessels, as it is more commonly present in specific regions of the body like parts of the male urethra and the conjunctiva of the eye.