Which atmospheric layer contains the majority of Earth's weather phenomena?

Correct Answer: A

Rationale: The troposphere, extending ~0-12 km above Earth's surface, contains ~80% of atmospheric mass and nearly all weather phenomena clouds, rain, storms driven by solar heating, convection, and water vapor. The stratosphere (~12-50 km) holds the ozone layer, stable and dry, with minimal weather. The mesosphere (~50-85 km) is cold, with rare noctilucent clouds, not typical weather. The thermosphere (~85-600 km) is thin, hot from solar radiation, and weatherless. The troposphere's density and dynamics (e.g., Hadley cells) foster weather, per meteorological data (e.g., AMS), making it the key layer, distinct from higher, less active regions.

Correct Answer: C

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

Correct Answer: C

Rationale: Ectoderm forms the epidermis (C), the skin's outer layer, via surface ectoderm differentiation into stratified squamous epithelium. Blood (A) originates from mesoderm, specifically hemangioblasts in the yolk sac and later bone marrow. The dermis (B), beneath the epidermis, is mesodermal, arising from fibroblasts and connective tissue. The spleen (D) is also mesodermal, from mesenchyme in the dorsal mesogastrium. C is correct epidermis' ectodermal lineage, forming skin and neural structures, distinguishes it from the mesodermal origins of the others.

Correct Answer: A

Rationale: Bowman's capsule, enclosing the glomerulus, is lined with simple squamous epithelium (A), thin for filtration of plasma into the nephron. Simple cuboidal (B) lines PCT, not capsule. Stratified squamous (C) is protective (e.g., skin), not filtration-suited. Transitional (D) stretches in the bladder, irrelevant here. A is correct simple squamous' flatness optimizes filtration, unlike the others' structures.