What is the largest muscle in the lower leg?

Correct Answer: B

Rationale: Gastrocnemius, spanning the calf, is the largest lower leg muscle, plantarflexing the foot with two heads. Soleus, beneath it, assists but is smaller. Tibialis anterior dorsiflexes, smaller and anterior. Tibialis posterior supports the arch, not largest. Gastrocnemius' bulk and power distinguish it, key for walking and jumping.

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.

Correct Answer: C

Rationale: Muscle names often reflect origin (fixed attachment) and insertion (movable end). Sternocleidomastoid specifies origins on the sternum and clavicle, inserting on the mastoid process of the temporal bone, guiding neck movement. Transversus abdominus denotes fibre direction and location, semimembranosus' implies membrane-like shape and location, and deltoid reflects its triangular shape. Only sternocleidomastoid explicitly ties to origin-insertion points, a naming style aiding anatomical precision, distinguishing it from shape-, action-, or location-based names in functional mapping.