At the end of quiet respiration, muscles are relaxed and lungs content represents.

Correct Answer: C

Rationale: After quiet expiration, respiratory muscles (diaphragm, intercostals) relax, and lungs settle at functional residual capacity (FRC, ~2.5-3 L), the resting volume where lung inward recoil equals chest wall outward recoil. Residual volume (RV, ~1-1.5 L) is post-maximal expiration, not quiet breathing. Expiratory reserve volume (ERV, ~1-1.5 L) is extra air forcibly exhaled, not the resting state. Inspiratory reserve volume (IRV, ~2-3 L) is additional inspiratory capacity, not post-expiration. FRC, with intra-alveolar pressure at atmospheric (~760 mmHg), is the passive equilibrium point, maintaining gas exchange readiness, distinct from volumes tied to forced maneuvers or inspiration, critical for respiratory baseline stability.

Correct Answer: D

Rationale: When inspiratory muscles (diaphragm, external intercostals) relax post-normal expiration, lungs reach functional residual capacity (FRC, ~2.5-3 L), the resting volume where lung and chest wall recoils balance, with no airflow (alveolar pressure = 760 mmHg). Vital capacity (VC, ~4-5 L) is maximal exhalable volume, requiring active inspiration false. Residual volume (RV, ~1-1.5 L) is post-maximal expiration false. Minimal volume' isn't standard, possibly RV or collapse (not natural) false. FRC is the passive rest state, key for gas exchange baseline, distinct from volumes tied to effort, making it the correct point of muscle relaxation.

Correct Answer: C

Rationale: Convection is the primary heat transfer mechanism from Earth's surface to the atmosphere. Solar radiation heats the surface (~168 W/m² absorbed), warming air via conduction (~24 W/m²), but convection dominates as warm air rises, transferring heat vertically (~97 W/m² latent + sensible heat, per energy budgets like Trenberth). Radiation (~396 W/m² emitted, ~333 W/m² back via greenhouse) is surface-to-space, not directly to atmosphere. Conduction is minor due to air's low conductivity. Advection moves heat horizontally, not vertically primary. Convection's buoyancy-driven circulation (e.g., thunderstorms) outpaces other modes, making it the key process, per climate models, for atmospheric heating.

Correct Answer: A

Rationale: The pterygopalatine fossa is a key junction. The maxillary artery enters via the pterygomaxillary fissure (A) from the infratemporal fossa, branching to supply the nose, palate, and pharynx. The maxillary nerve (V2) enters from the middle cranial fossa (C) through the foramen rotundum, exiting variably (e.g., infraorbital canal, D, for the face). At the pterygomaxillary fissure (A), the artery enters while the nerve is already within, heading elsewhere, fulfilling different directions.' B (infratemporal fossa) is the artery's origin, not passage point; C and D are partial paths, not the junction. A is the precise anatomical site of divergence.

Correct Answer: D

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.