**Core Concept**
Complex polysaccharides, such as starches and glycogen, need to be broken down into simpler sugars like glucose for absorption in the small intestine. This process involves the action of specific enzymes that cleave the glycosidic bonds between sugar molecules.

**Why the Correct Answer is Right**
Sucrase is a disaccharidase enzyme that specifically breaks down sucrose (table sugar) into glucose and fructose. It is a key component of the brush border membrane in the small intestine, where it facilitates the hydrolysis of sucrose into its constituent sugars. This allows glucose to be absorbed through the intestinal epithelial cells into the bloodstream. The presence of sucrase in the small intestine enables the body to utilize dietary sucrose as a source of energy.

**Why Each Wrong Option is Incorrect**
**Option A:** Na+k+ATPase is a membrane-bound enzyme involved in the active transport of sodium and potassium ions across cell membranes, particularly in the kidneys and the cardiac muscle cells. It is not directly involved in the breakdown or absorption of complex polysaccharides.

**Option C:** Enterokinase, also known as enteropeptidase, is an enzyme produced by the cells of the duodenum that activates trypsinogen (a zymogen) to trypsin, an enzyme essential for protein digestion. It is not involved in the breakdown of complex polysaccharides.

**Option D:** Carboxypeptidase is a type of exopeptidase enzyme that cleaves the C-terminal amino acid from a polypeptide chain. It is involved in protein digestion, particularly in the breakdown of peptides into individual amino acids, rather than the breakdown of complex polysaccharides.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the small intestine has a specific arrangement of enzymes in its brush border membrane, including sucrase, maltase, and lactase, which work together to break down dietary carbohydrates into simple sugars for absorption.

**✓ Correct Answer: B. Sucrase**