Correct Answer: B

Rationale: A) Ribosome: Ribosomes are cellular organelles responsible for protein synthesis and are not directly involved in controlling the progression of mitosis. B) Cyclin-dependent kinase (CDK): CDKs are a family of protein kinases that regulate the cell cycle, including the progression of mitosis. CDK activity is controlled by cyclins, which bind to CDKs to activate them at specific points in the cell cycle. The activation and degradation of cyclins regulate the activity of CDKs, which in turn control the progression of mitosis. C) Centriole: Centrioles are involved in organizing the microtubules of the mitotic spindle but do not directly control the progression of mitosis. D) Microtubule: Microtubules are structural components of the cytoskeleton and are involved in various cellular processes, including mitosis, but they do not control

Correct Answer: D

Rationale: Elasticity refers to a material's ability to resist deformation and return to its original shape after stress is applied. It is the property that resists a change in shape. Density is the mass per unit volume of a substance. Mass is the amount of matter in an object, while inertia is the tendency of an object to resist changes in its state of motion. Viscosity, not mentioned in the question, is the resistance of a fluid to flow, not shape change.

Correct Answer: B

Rationale: B) Commensalism: In commensalism, one organism benefits while the other is neither helped nor harmed. This is the relationship described in the question. The correct answer is Commensalism because it specifically fits the scenario where one organism benefits without affecting the other. A) Mutualism: In mutualism, both organisms involved benefit from the relationship. C) Parasitism: In parasitism, one organism benefits at the expense of the other organism, which is harmed. D) Predation: In predation, one organism (predator) kills and consumes another organism (prey) for food.

Correct Answer: C

Rationale: Ribosomal RNA (rRNA) plays a crucial role in forming the structural framework of ribosomes. Ribosomes are the cellular organelles responsible for protein synthesis and consist of both protein and rRNA components. The primary function of rRNA is to provide the structural support necessary for ribosomes to function properly. This structural framework allows the ribosome to interact with messenger RNA (mRNA) and transfer RNA (tRNA) during translation, where genetic information encoded in mRNA is used to assemble proteins from amino acids. Therefore, rRNA's main role is in contributing to the structure and function of ribosomes, rather than directly carrying amino acids, reading the genetic code, or controlling the rate of protein synthesis. Choices A, B, and D are incorrect because rRNA does not carry amino acids to the ribosomes (tRNA does this), read the genetic code (this is the role of ribosomes and tRNA), or control the rate of protein synthesis (this is regulated by various factors but not directly by rRNA).

Correct Answer: B

Rationale: In a balanced chemical equation, the number of atoms of each element must be the same on both sides of the equation. When sodium (Na) reacts with chlorine (Cl2) to form sodium chloride (NaCl), we need to ensure the equation is balanced. There are 2 chlorine atoms in Cl2; hence, we need 2 sodium atoms on the left side to balance it. Therefore, the balanced chemical equation is 2Na + Cl2 -> 2NaCl. Choice A is incorrect because it does not have the correct coefficients to balance the equation. Choice C is incorrect as it incorrectly represents the formula of sodium. Choice D is incorrect as it forms NaCl2, which is not the correct compound formed in this reaction.