The cardiac output is

Correct Answer: C

Rationale: Cardiac output (CO) is heart rate (HR) times stroke volume (SV). Given HR = 84 bpm and SV = 60 ml (0.06 L), CO = 84 × 0.06 = 5.04 L/min, approximated as 5 L/min. '5 L/min,' is correct, per physiology (e.g., Guyton). The question's exercise scenario (13 L/min) is post-exercise, but initial CO aligns with resting values. Choices A, B, and D miscalculate. C's accuracy makes it the answer.

Correct Answer: B

Rationale: The uterine (fallopian) tube is about 10 cm long, extending from ovary to uterus. '10 cm,' is correct, per anatomy texts like Netter's Atlas, varying slightly (7-12 cm) but typically cited as 10 cm. '5 cm,' is too short. '15 cm,' and '20 cm,' exceed average length. The tube's role in ovum transport supports B's accuracy, reflecting standard anatomical measurements.

Correct Answer: C

Rationale: Essential amino acids must be dietary, as the body cannot synthesize them. 'Alanine,' is correct as the exception, a non-essential amino acid produced from pyruvate, per biochemistry (e.g., Nelson). 'Leucine,' 'Lysine,' and 'Valine,' are essential, required from food. Alanine's endogenous synthesis contrasts with the dietary need for others, making C the precise answer.

Correct Answer: C

Rationale: Villi are the small intestine's functional units, maximizing absorption. 'Villi,' is correct, per histology (e.g., Ross), with enterocytes for digestion and uptake. 'Mucosa,' is a layer containing villi. 'Muscularis,' aids motility. 'Serosa,' is the outer layer. Villi's absorptive role makes C the precise answer.

Correct Answer: B

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