A dependent variable is

Correct Answer: B

Rationale: A dependent variable is the outcome measured in research, affected by the independent variable. 'An effect variable,' is correct, aligning with experimental design (e.g., Campbell & Stanley), where it reflects changes (e.g., pain level post-treatment). 'Manipulated,' describes the independent variable. 'An intervention variable,' is also independent. 'An interdependent variable,' is not standard; variables may correlate, but dependent' means effected. B's focus on the variable being influenced matches its role, making it the precise answer.

Correct Answer: B

Rationale: The SA node's pacemaker potential results from calcium influx via T-type channels, depolarizing cells. 'Calcium,' is correct, per cardiac physiology (e.g., Opie). 'Sodium,' contributes later in action potentials. 'Potassium,' hyperpolarizes. 'Magnesium,' is minor. Calcium's role in phase 4 depolarization makes B the precise answer.

Correct Answer: C

Rationale: Parathyroid hormone (PTH) increases plasma calcium by mobilizing bone calcium and renal reabsorption when levels drop. 'Parathyroid hormone,' is correct, per endocrinology texts like Williams, countering hypocalcemia. 'Calcitonin,' lowers calcium, opposing PTH. 'Aldosterone,' regulates sodium, not calcium directly. 'Adrenaline,' affects metabolism, not calcium. PTH's specific response to low calcium, restoring balance, makes C the precise answer, rooted in calcium homeostasis.

Correct Answer: B

Rationale: Oogenesis is the formation of ova (eggs) in the ovaries, from oogonia to mature oocytes. 'Oogenesis,' is correct, per reproductive physiology (e.g., Tortora). 'Spermatogenesis,' is sperm formation. 'Ovulation,' is egg release. 'Fertilization,' is conception. Oogenesis' full developmental process makes B the accurate answer, specific to female gametes.

Correct Answer: B

Rationale: The loop of Henle extends into the renal medulla, creating a concentration gradient for urine. 'Loop of Henle,' is correct, per anatomy texts like Moore, with its descending and ascending limbs medullary. 'Proximal convoluted tubule,' and 'Distal convoluted tubule,' are cortical. 'Bowman's capsule,' is in the cortex. The loop's medullary location distinguishes B as the accurate answer.