According to the ASA physical status classification system, patients with severe systemic disease that is a constant threat to life are categorized as

Correct Answer: D

Rationale: The ASA classification assesses patient risk before anesthesia. 'ASA PS 4,' is correct for patients with severe systemic disease posing a constant life threat (e.g., unstable angina), per ASA guidelines. 'ASA PS 3,' is severe disease without immediate danger (e.g., stable diabetes). 'ASA PS 2,' is mild systemic disease (e.g., controlled hypertension). 'ASA PS 5,' is moribund patients unlikely to survive 24 hours. ASA PS 4's focus on life-threatening conditions matches the description, making D the precise answer.

Correct Answer: B

Rationale: Reliability, consistency of measurement, is tested via a pilot study. 'Pilot study,' is correct because it assesses tool reliability (e.g., test-retest), per research methods (e.g., Cronbach). 'Carefully designed questionnaire,' aids reliability but doesn't test it. 'Hypothesis testing,' evaluates validity, not consistency. 'Data analysis,' interprets results, not reliability. Pilot studies' role in pre-testing reliability distinguishes B as the accurate answer.

Correct Answer: B

Rationale: Cardiac reserve is the difference between maximum cardiac output (CO) during exercise and resting CO. Resting CO = 84 × 0.06 = 5 L/min; exercise CO = 13 L/min. Reserve = 13 - 5 = 8 L/min. '8 L/min,' is correct, per cardiovascular physiology (e.g., Berne & Levy). Choice A is exercise CO, not reserve. Choice C and D misalign. B's calculation fits, making it the answer.

Correct Answer: B

Rationale: Iodine is essential for thyroid hormone synthesis (T3 and T4), regulating metabolism. 'Iodine,' is correct, per endocrinology texts like Williams' Textbook of Endocrinology, where iodine deficiency disrupts metabolic rate. 'Iron,' is in hemoglobin, not thyroid-specific. 'Calcium,' affects bones and signaling, not metabolism via thyroid. 'Magnesium,' supports enzymatic function, not thyroid-related metabolism. Iodine's incorporation into thyroxine, directly influencing basal metabolic rate, makes B the precise answer, critical to thyroid physiology.

Correct Answer: C

Rationale: Oxytocin, from the posterior pituitary, triggers milk ejection by contracting myoepithelial cells in the breast. 'Oxytocin,' is correct, per physiology texts like Costanzo, distinct from milk production. 'Progesterone,' supports pregnancy, not ejection. 'Prolactin,' stimulates milk synthesis. 'Oestrogen,' aids breast development. Oxytocin's specific let-down reflex role makes C the accurate answer, critical in lactation.