**Core Concept**
The patient is experiencing hypoglycemia due to the combination of insulin and acarbose, highlighting the importance of understanding the mechanism of action of these medications. Insulin lowers blood glucose by facilitating glucose uptake in cells, while acarbose inhibits intestinal alpha-glucosidases, preventing carbohydrate absorption.

**Why the Correct Answer is Right**
Acarbose works by inhibiting the enzyme alpha-glucosidase, which breaks down complex carbohydrates into simple sugars. However, in the presence of acarbose, unabsorbed carbohydrates can be fermented by gut bacteria, producing short-chain fatty acids and increasing blood glucose levels. Therefore, administering glucose or a rapidly absorbed carbohydrate is essential to rapidly correct hypoglycemia in this patient. Glucagon, option D, can also be used but is less suitable as it would require parenteral administration and may not be readily available.

**Why Each Wrong Option is Incorrect**
**Option A:** Glucagon is not the best choice in this scenario as it would require parenteral administration and may not be readily available.
**Option B:** Glucagon is not the best choice in this scenario as it would require parenteral administration and may not be readily available.

**Clinical Pearl / High-Yield Fact**
In patients taking acarbose, administering glucose or rapidly absorbed carbohydrates is crucial to treat hypoglycemia, as unabsorbed carbohydrates can be fermented by gut bacteria, producing short-chain fatty acids and increasing blood glucose levels.

**Correct Answer:** D. Glucagon.