Nokea
Salts are formed by the reaction between:
- A. Two acids
- B. An acid and a base
- C. Two bases
- D. A metal and a nonmetal only
Correct Answer: B
Rationale: Salts are formed by the reaction between an acid and a base. This reaction is known as a neutralization reaction. In this reaction, the acid donates a proton (H+) to the base, resulting in the formation of water and a salt as the products. Choice A is incorrect because salts are not formed by the reaction of two acids. Choice C is incorrect as salts are not produced by the reaction of two bases. Choice D is incorrect because while salts can be formed from the reaction between a metal and a nonmetal, it is not the only way salts are produced.
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What is the role of RNA interference in silencing genes?
- A. Increases protein production
- B. Promotes gene mutation
- C. Inhibits the expression of specific genes
- D. Repairs damaged DNA
Correct Answer: C
Rationale: RNA interference (RNAi) is a biological process that involves the silencing of gene expression by inhibiting the translation of mRNA or by degrading mRNA molecules. This mechanism plays a crucial role in regulating gene expression and can be used to selectively silence specific genes. By interfering with the expression of specific genes, RNAi can downregulate protein production from those genes. Therefore, option C, 'Inhibits the expression of specific genes,' is the correct role of RNA interference in silencing genes. Options A, B, and D are incorrect because RNA interference does not increase protein production, promote gene mutation, or repair damaged DNA; its primary function is to inhibit gene expression by degrading or interfering with mRNA.
What is the formula to calculate kinetic energy?
- A. Kinetic Energy = Mass Velocity
- B. Kinetic Energy = Force Distance
- C. Kinetic Energy = Power Time
- D. Kinetic Energy = Potential Energy · Time
Correct Answer: A
Rationale: Kinetic energy is the energy an object possesses due to its motion. The formula to calculate kinetic energy is KE = 0.5 mass velocity^2, which can also be written as KE = mass (velocity)^2. Therefore, the correct formula is Kinetic Energy = Mass Velocity. Choice B is incorrect because it represents the work formula. Choice C is incorrect as it represents the formula for work done. Choice D is incorrect as it does not accurately represent the formula for calculating kinetic energy.
Which group of elements is known for their reactivity and ability to form strong bonds with other elements?
- A. Noble gases
- B. Halogens
- C. Alkali metals
- D. Transition metals
Correct Answer: B
Rationale: Halogens are a group of elements in the periodic table known for their high reactivity and ability to form strong bonds with other elements. They possess seven valence electrons, requiring only one more electron to achieve a stable electron configuration, making them highly reactive. Halogens readily form compounds with other elements by gaining an electron to achieve a full outer shell, resulting in the formation of strong covalent bonds. Noble gases (option A), on the other hand, are known for their inertness and stable electron configurations, making them unlikely to form bonds. Alkali metals (option C) are highly reactive but do not form bonds as strong as halogens. Transition metals (option D) are recognized for their variable oxidation states and ability to create complex ions but are not as reactive as halogens when it comes to bond formation.
Neurons, the functional units of the nervous system, belong to which tissue type?
- A. Epithelial tissue
- B. Connective tissue
- C. Muscle tissue
- D. Nervous tissue
Correct Answer: D
Rationale: Neurons are the functional units of the nervous system and are specialized cells that transmit nerve impulses. They belong to nervous tissue, which is the primary tissue type of the nervous system. Nervous tissue is composed of neurons and supporting cells called neuroglia. Choices A, B, and C are incorrect because epithelial tissue functions mainly in covering and lining body surfaces, connective tissue provides support and structure, and muscle tissue is responsible for movement. Neurons, being the basic functional units of the nervous system, are specifically classified under nervous tissue.
A car skids on a wet road. What is the main force preventing the car from stopping?
- A. Friction
- B. Gravitational force
- C. Normal force from the road
- D. Air resistance
Correct Answer: A
Rationale: The correct answer is A: Friction. Friction is the force that opposes the motion of the car on the wet road surface, making it harder for the car to stop. When the car skids, the friction between the tires and the wet road surface is reduced, leading to a loss of traction and making it challenging for the car to come to a halt. Gravitational force (choice B) is the force that pulls objects toward each other due to gravity and does not directly impact the car's ability to stop on a wet road. The normal force from the road (choice C) is the force exerted by the road surface perpendicular to the car's tires and does not play a significant role in stopping the car. Air resistance (choice D) is the force that opposes the motion of an object through the air, but it is not the main force preventing the car from stopping on a wet road.