**Core Concept**
The kidney's glomerular filtration barrier is a selective filter that restricts the passage of certain molecules based on their size, charge, and molecular weight. This selective permeability is crucial for maintaining proper electrolyte balance, preventing excessive fluid loss, and regulating the composition of the urine.

**Why the Correct Answer is Right**
The glomerular filtration barrier primarily restricts the passage of large molecules, such as proteins, and negatively charged substances, like albumin. This is achieved through the presence of negatively charged glycoproteins, like nephrin and podocalyxin, which line the glomerular basement membrane. Additionally, the filtration slits between the podocytes prevent the passage of large molecules, ensuring that the filtrate is rich in small molecules, like water, ions, and glucose.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is often a distractor, but it is not a correct answer. While it is true that the kidney restricts the passage of certain substances, this option is not the most accurate representation of the kidney's selectivity.

**Option B:** This option is incorrect because proteins, including albumin, are normally restricted from passing through the glomerular filtration barrier. However, in certain conditions, like nephrotic syndrome, the barrier can be compromised, allowing proteins to pass through.

**Option C:** This option is incorrect because glucose is actually freely filtered through the glomerular filtration barrier, with minimal restriction.

**Option D:** This option is incorrect because water is freely filtered through the glomerular filtration barrier, with minimal restriction.

**Clinical Pearl / High-Yield Fact**
In the context of kidney disease, it is essential to remember that the glomerular filtration barrier's selectivity can be compromised, leading to the loss of large molecules in the urine, such as proteins in nephrotic syndrome.

**Correct Answer:** B.