What is the action of the masseter?

Correct Answer: B

Rationale: The masseter, from zygomatic arch to mandible, elevates the jaw, closing it for chewing, a primary masticatory muscle. Swallowing involves pharyngeal muscles (e.g., constrictors). Lip movement uses orbicularis oris. Eye closure is orbicularis oculi's role. Masseter's powerful jaw elevation distinguishes it, key for biting and grinding, unlike swallowing, lip, or eye actions.

Correct Answer: B

Rationale: Chloroplasts, organelles containing chlorophyll, enable organisms to perform photosynthesis, converting sunlight, carbon dioxide, and water into glucose. Organisms with chloroplasts, like plants and algae, are autotrophs, producing their own food. Heterotrophs, such as animals, consume others for energy, lacking chloroplasts. Herbivores eat plants but don't photosynthesize, and primary consumers occupy an ecological role, not a metabolic one. Autotrophs' self-sustaining capability, reliant on chloroplasts, sets them apart, aligning with their role as producers in ecosystems and their cellular structure.

Correct Answer: C

Rationale: Work in physics is force times distance. Both lifted identical chairs the same vertical distance, applying equal force against gravity (the chair's weight). Age or strength doesn't alter the chair's mass or height moved, so work done is identical. Without data on differing distances or forces like lifting speed or extra effort both perform equal work. This reflects work's definition, focusing on displacement and force, not individual capacity, making their efforts mechanically equivalent.

Correct Answer: D

Rationale: In a closed container with fixed volume, Gay-Lussac's law states pressure rises with temperature. Warming hydrogen from 20°C to 25°C increases molecular kinetic energy, causing more frequent, forceful collisions with container walls. Pressure, the force per area, thus increases proportionally (P ∝ T in Kelvin: 293K to 298K). It doesn't stay constant, decrease, or fluctuate without volume change. This pressure rise, a gas law fundamental, reflects temperature's direct impact on confined gas behavior.

Correct Answer: D

Rationale: Thick filaments in sarcomeres are composed of myosin, with heads forming cross-bridges to pull actin during contraction, creating the A band's density. Troponin and tropomyosin, regulatory proteins, pair with actin in thin filaments, not thick. Actin forms thin filaments, overlapping myosin, not constituting thick ones. Myosin's exclusive role in thick filaments drives force generation, distinguishing it from thin filament components, fundamental to muscle contraction mechanics.