Which of the following gases is the most abundant in Earth's atmosphere?

Correct Answer: B

Rationale: Nitrogen (N2) is the most abundant gas in Earth's atmosphere, comprising ~78% by volume, due to its chemical stability and geological accumulation. Oxygen (O2) is ~21%, vital for life but secondary. Argon (~0.93%) and carbon dioxide (CO2, ~0.0407%) are trace gases, with CO2 critical for climate despite low abundance. Nitrogen's dominance results from its inert nature and massive release during Earth's formation, per atmospheric composition data (e.g., NOAA). It dilutes other gases, shaping atmospheric pressure (~1013 hPa), making it the correct choice, far exceeding oxygen or trace constituents in prevalence.

Correct Answer: B

Rationale: Terminal bronchioles (B) lack goblet cells, lined by simple cuboidal with club cells, unlike olfactory (A, specialized), epiglottis (C), and false cords (D). B is the exception.

Correct Answer: C

Rationale: Neural crest cells, an ectodermal derivative, give rise to melanocytes (A), Schwann cells (B), and adrenal medulla (D). Melanocytes produce pigment, Schwann cells myelinate peripheral nerves, and the adrenal medulla forms chromaffin cells for adrenaline. Pia mater (C), the innermost meninges, derives from neural tube mesenchyme (possibly mesodermal or ectodermal, but not neural crest). Neural crest contributes to peripheral nervous system and pigment cells, not central meninges. C is the exception its origin outside neural crest lineage distinguishes it from the others.

Correct Answer: C

Rationale: Primary oocytes are surrounded by zona pellucida (A) and enter meiosis I prenatally (B), arresting until puberty. Meiosis I completes at ovulation (not puberty, C), forming a secondary oocyte, which completes meiosis II post-fertilization (D). C is false meiosis I finishes at ovulation, not puberty, making it the exception.