Correct Answer: A

Rationale: The correct answer is A: The centrioles. Centrioles are cylindrical structures found in animal cells that are crucial in organizing the spindle fibers during cell division (mitosis). They play a vital role in separating chromosomes during cell division, ensuring each daughter cell receives the correct number of chromosomes. Additionally, centrioles are involved in the formation of cilia and flagella, essential for cell motility and sensory functions. The nucleolus is responsible for ribosome production, the Golgi apparatus processes and packages proteins, and the endoplasmic reticulum is involved in protein synthesis and lipid metabolism. These structures do not have a direct role in controlling the cell cycle and preventing uncontrolled cell growth.

Correct Answer: D

Rationale: Beta waves, associated with alertness and focused attention, typically fall within the range of 13-30 Hz. These waves are present when individuals are engaged in cognitive tasks, problem-solving, or focused mental activities. Options A, B, and C are incorrect because these frequency ranges are not characteristic of beta waves. Beta waves are higher in frequency and are associated with more active mental states compared to the ranges mentioned in options A, B, and C. Therefore, the correct answer is 13-30 Hz (Choice D).

Correct Answer: B

Rationale: Sodium chloride (table salt) is typically a good conductor of electricity when dissolved in water because it dissociates into ions (sodium cations and chloride anions) that can carry an electric current. Sugar (choice A), olive oil (choice C), and oxygen gas (choice D) do not dissociate into ions in water and therefore are not good conductors of electricity. Sugar does not dissociate into ions in water, so it cannot conduct electricity. Olive oil and oxygen gas are nonpolar substances and do not ionize in water, making them poor conductors of electricity.

Correct Answer: B

Rationale: Cartilage is a type of connective tissue that provides support and flexibility to various parts of the body, such as joints and the ear. It is composed of cells called chondrocytes embedded in a matrix of collagen and proteoglycans. Epithelial tissue covers body surfaces, muscle tissue is involved in movement, and nervous tissue transmits signals. The correct answer is connective tissue because cartilage serves a supportive function in the body.

Correct Answer: B

Rationale: A) Incorrect. DNA is double-stranded, but RNA is typically single-stranded. B) Correct. DNA contains deoxyribose sugar, which lacks an oxygen atom on the 2' carbon of the sugar ring, while RNA contains ribose sugar, which has an additional hydroxyl group on the 2' carbon. C) Incorrect. RNA contains the nitrogenous base uracil, while DNA contains thymine. D) Incorrect. DNA and RNA have distinct structures and functions, so they are not identical molecules.