**Core Concept**
Glucose co-transport with Na+ ions is a type of secondary active transport that involves the movement of glucose against its concentration gradient using the energy generated from the movement of Na+ ions down their concentration gradient. This process is crucial for the absorption of glucose in the intestines and kidneys.

**Why the Correct Answer is Right**
The co-transport of glucose with Na+ ions occurs through the SGLT (Sodium-Glucose Linked Transporter) proteins, primarily SGLT1 in the small intestine and SGLT2 in the kidneys. These proteins have two binding sites: one for glucose and another for Na+ ions. The binding of Na+ ions to SGLT proteins causes a conformational change that facilitates the binding and subsequent transport of glucose into the cell against its concentration gradient. This process is essential for glucose absorption in the intestines and reabsorption in the kidneys.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the co-transport of glucose with Na+ ions. The co-transport of glucose with Na+ ions is a type of secondary active transport, not facilitated diffusion.
**Option B:** This option is incorrect because the co-transport of glucose with Na+ ions is not an example of primary active transport. Primary active transport requires the direct use of ATP to transport molecules against their concentration gradient, whereas secondary active transport uses the energy generated from the movement of another molecule down its concentration gradient.
**Option D:** This option is incorrect because the co-transport of glucose with Na+ ions is not an example of passive transport. Passive transport involves the movement of molecules down their concentration gradient without the use of energy, whereas secondary active transport uses the energy generated from the movement of another molecule down its concentration gradient.

**Clinical Pearl / High-Yield Fact**
In the kidneys, the reabsorption of glucose is crucial to prevent glucose loss in the urine. The maximum reabsorption capacity of the kidneys for glucose is approximately 180 mg/dL. When blood glucose levels exceed this threshold, glucose appears in the urine, leading to glycosuria.

**Correct Answer: C. Secondary Active Transport**