The approximate gestation period in human is

Correct Answer: B

Rationale: Human gestation averages 280 days (40 weeks) from the last menstrual period (LMP). '280 days,' is correct, per obstetrics texts like Williams Obstetrics, a standard clinical estimate. '250 days,' is about 36 weeks, preterm. '300 days,' (43 weeks) and '320 days,' (46 weeks) exceed typical full-term. The 280-day norm, aligning with fetal development, makes B the precise answer, widely accepted in medical practice.

Correct Answer: D

Rationale: Accessory digestive organs aid digestion outside the alimentary canal. 'Kidney,' is correct as the exception, filtering blood, not digesting, per physiology (e.g., Guyton). 'Liver,' produces bile. 'Pancreas,' secretes enzymes. 'Gall bladder,' stores bile. Kidney's excretory role distinguishes D as the accurate answer.

Correct Answer: C

Rationale: The peripheral nervous system (PNS) includes nerves outside the CNS. 'Spinal cord,' is correct as the exception, part of the CNS, per anatomy (e.g., Tortora). 'Cranial nerves,' and 'Spinal nerves,' are PNS. 'Autonomic nervous system,' is PNS's involuntary arm. Spinal cord's CNS role makes C the accurate answer.

Correct Answer: B

Rationale: The diaphragm is the primary muscle dividing thoracic and abdominal cavities, aiding respiration. 'Diaphragm,' is correct, per anatomy (e.g., Moore). 'Intercostal,' assists breathing between ribs. 'Rectus abdominis,' is abdominal. 'Pectoralis major,' is chest. Diaphragm's septal role makes B the accurate answer.

Correct Answer: D

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