**Core Concept**
Bone metabolism is tightly regulated by hormones, growth factors, and vitamins. Abnormalities in bone metabolism can occur due to excess or deficiency of various vitamins, which can affect bone health by influencing osteoblast and osteoclast activity.

**Why the Correct Answer is Right**
Excess of vitamin A and D can lead to abnormalities in bone metabolism. Vitamin A excess can cause increased osteoclast activity, leading to bone resorption and increased bone turnover. Similarly, excess of vitamin D can cause increased bone resorption and deposition of calcium in soft tissues, leading to conditions like hypercalcemia and calcification of joints. Both vitamins play crucial roles in bone health, and their excess can disrupt normal bone metabolism.

**Why Each Wrong Option is Incorrect**
* **Option A:** While vitamin C is essential for collagen synthesis and bone health, excess of vitamin C is not typically associated with abnormalities in bone metabolism.
* **Option B:** Vitamin B12 is crucial for DNA synthesis and nerve function, but its excess is not directly linked to bone metabolism abnormalities.
* **Option C:** Vitamin E is an antioxidant that protects cells from damage, but its excess is not typically associated with bone metabolism abnormalities.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that excessive intake of vitamins A and D can lead to bone metabolism abnormalities, and monitoring vitamin levels is crucial in patients with conditions like hyperparathyroidism or osteoporosis.

**Correct Answer:** A. Excess of vitamins A and D.