Which statement about the appliance must be correct?

Correct Answer: D

Rationale: The correct answer is D: It is double-insulated. This is correct because double-insulated appliances have an extra layer of insulation for added safety, eliminating the need for a grounded connection. This feature protects users from electric shocks. Explanation for why the other choices are incorrect: A: It does not have a live connection - This is not necessarily true as appliances can have live connections depending on their design and function. B: It has two fuses - While some appliances may have fuses, the number of fuses does not determine the correctness of the statement about the appliance. C: It has two switches - The presence of two switches does not necessarily indicate the correctness of the statement about the appliance.

Correct Answer: D

Rationale: Osteitis fibrosa cystica is caused by an increase in the parathyroid hormone (PTH). Elevated PTH levels lead to increased calcium release from bones, resulting in bone resorption and cyst formation. Other choices (A) calcitonin, (B) ADH, and (C) growth hormone do not directly impact calcium metabolism and bone resorption like PTH does.

Correct Answer: C

Rationale: The correct answer is C because the release of hormones by the parathyroid glands is actually controlled by the levels of calcium in the blood, not by the pituitary gland. A: True - Parathyroid glands are four small yellowish brown ovoid glands. B: True - They lie in relation to the posterior border of thyroid lobes. D: True - The hormone produced by the parathyroid glands, parathyroid hormone (PTH), controls blood calcium levels by stimulating the release of calcium from bones and increasing the absorption of calcium from the intestines.

Correct Answer: d

Rationale: Rationale for Correct Answer (D): 1. Ca2+ ions do not directly break down ATP into ADP + inorganic phosphate at the sarcomere. 2. This breakdown occurs through the enzymatic action of myosin ATPase. 3. Ca2+ ions primarily bind to troponin to initiate muscle contraction by moving tropomyosin. 4. Ca2+ ions help expose active sites on actin, facilitating cross-bridge formation. Summary of Incorrect Choices: A. Correct - Ca2+ binds to troponin to move tropomyosin, not to uncover it. B. Correct - Ca2+ aids in exposing active sites on actin, not troponin. C. Correct - Ca2+ is stored in the sarcoplasmic reticulum, but it is released into the cytoplasm to trigger muscle contraction, not stored in the terminal cisternae.

Correct Answer: A

Rationale: Step-by-step rationale for choice A being correct: 1. ADH and oxytocin are peptide hormones. 2. They are synthesized in the hypothalamus. 3. They are transported and stored in the neurohypophysis. 4. Upon stimulation, they are released from the neurohypophysis. 5. Therefore, both ADH and oxytocin are indeed secreted by the neurohypophysis. Summary of why other choices are incorrect: B: ADH and oxytocin are not mineralocorticoids; they regulate water balance and uterine contractions, respectively. C: Islets of Langerhans secrete insulin and glucagon, not ADH or oxytocin. D: ADH promotes water reabsorption in the kidneys, opposite to excreting Na+ and water.