**Core Concept**
Patient presents with perioral paresthesia and hypocalcemia (serum calcium level of 7 mg/dL) after thyroid surgery, likely due to accidental injury to the parathyroid glands during surgery. This condition is a classic example of hypoparathyroidism, which results from inadequate parathyroid hormone (PTH) secretion.

**Why the Correct Answer is Right**
The best management for hypocalcemia after thyroid surgery involves administering calcium supplements to correct the serum calcium level. This is because the parathyroid glands are responsible for regulating calcium levels in the body by secreting PTH, which stimulates the release of calcium from bone stores and increases its absorption from the gut. Without adequate PTH, calcium levels drop, leading to symptoms such as perioral paresthesia. Administering calcium supplements helps to rapidly correct the serum calcium level and alleviate symptoms.

**Why Each Wrong Option is Incorrect**
**Option A:** Administering vitamin D supplements alone would not be sufficient to correct hypocalcemia in this scenario, as vitamin D is necessary for calcium absorption, but calcium levels need to be replenished immediately to alleviate symptoms.

**Option B:** Administering a calcium channel blocker would worsen hypocalcemia by inhibiting calcium entry into cells.

**Option C:** Administering a diuretic would also worsen hypocalcemia by increasing urinary calcium excretion.

**Clinical Pearl / High-Yield Fact**
To prevent hypocalcemia after thyroid surgery, it's essential to identify and preserve the parathyroid glands during surgery, and to closely monitor serum calcium levels post-operatively.

**Correct Answer:** A. Administer calcium supplements to correct serum calcium level.