Correct Answer: B

Rationale: The correct answer is B: Mitochondria. Mitochondria are known as the powerhouses of the cell and are responsible for producing energy in the form of ATP through cellular respiration. ATP is the primary energy currency of the cell, powering various cellular activities. The nucleus (choice
A) is responsible for housing the cell's genetic material but is not involved in ATP production. Ribosomes (choice
C) are involved in protein synthesis, not energy production. The Golgi apparatus (choice
D) is responsible for modifying, sorting, and packaging proteins for secretion, not for ATP production.

Correct Answer: B

Rationale: The correct answer is B. Arteries carry oxygenated blood away from the heart to the rest of the body, delivering nutrients and oxygen to the tissues. Veins, on the other hand, carry deoxygenated blood back to the heart. Capillaries are where the exchange of gases, nutrients, and waste products occurs between the blood and tissues. Lymphatic vessels are responsible for transporting lymph, which is a clear fluid containing white blood cells and waste products, and play a key role in the immune system.

Correct Answer: A

Rationale: Hydroxyapatite is a mineral compound composed of calcium and phosphorus that plays a crucial role in strengthening the collagen matrix of bones, contributing to their structural integrity and hardness. It is a key component of bone tissue and provides the mineralization necessary for bone strength and density.
Choice B is incorrect because the structural unit of a bone is the osteon or Haversian system, not hydroxyapatite.
Choice C is incorrect as it describes cartilage, not hydroxyapatite.
Choice D is incorrect as it refers to the epiphysis, which is not synonymous with hydroxyapatite.

Correct Answer: A

Rationale: An atom's charge is determined by the difference between the number of protons and electrons. Since the atom has 17 protons and 19 electrons, the net charge is positive. The excess of two electrons compared to protons results in a positive charge.
Choice B (Negative) is incorrect because the atom has more protons than electrons, leading to a positive charge.
Choice C (Neutral) is incorrect because the atom has an imbalance between protons and electrons, resulting in a charge.
Choice D (Cannot be determined) is incorrect as the charge can be determined based on the given information.

Correct Answer: A

Rationale: The correct answer is A: Noble gases are non-reactive because they have a full valence shell with 8 electrons, making them stable and unlikely to form chemical bonds with other elements.
Choice B is incorrect because Noble gases are known for their inertness and lack of reactivity.
Choice C is incorrect because Noble gases have 8 valence electrons, which is a key characteristic that contributes to their stability.
Choice D is incorrect because Noble gases have 8 valence electrons, not 7.