**Core Concept**
The question is testing the knowledge of a specific disaccharidase enzyme, which is a type of carbohydrate digestive enzyme. Disaccharidases are enzymes that break down disaccharides (sugars composed of two monosaccharides) into simpler monosaccharides that can be absorbed by the body.

**Why the Correct Answer is Right**
The correct answer is **Lactase**, an enzyme that specifically breaks down lactose (a disaccharide composed of glucose and galactose) into glucose and galactose. This enzyme is present in the small intestine and plays a crucial role in the digestion of lactose-containing dairy products. Lactase works by cleaving the glycosidic bond between glucose and galactose, resulting in the production of these two simple sugars that can be absorbed by the body.

**Why Each Wrong Option is Incorrect**
**Option A:** **Maltase** is an enzyme that breaks down maltose (a disaccharide composed of two glucose molecules) into glucose, but it is not the correct answer to this question.
**Option B:** **Sucrase** is an enzyme that breaks down sucrose (a disaccharide composed of glucose and fructose) into glucose and fructose, but it is not the correct answer to this question.
**Option C:** **Trehalase** is an enzyme that breaks down trehalose (a disaccharide composed of two glucose molecules) into glucose, but it is not the correct answer to this question.

**Clinical Pearl / High-Yield Fact**
Lactose intolerance is a condition where individuals have a deficiency of lactase enzyme, leading to symptoms such as bloating, gas, diarrhea, and abdominal cramps after consuming lactose-containing dairy products. This condition is relatively common worldwide and can be managed with dietary modifications or lactase enzyme supplements.

**Correct Answer: D. Lactase**