**Core Concept:** Glomerular filtration is the process by which essential substances are allowed to pass through the glomerular capillary wall into the renal tubules. The glomerular membrane is composed of fenestrated endothelial cells, podocytes, and a basement membrane. The filtration rate is determined by the size, charge, and hydrophobicity of the substance.

**Why the Correct Answer is Right:** Substances that can pass through the glomerular membrane are classified as "filterable." Filterable substances are small, uncharged, and hydrophilic. This means they are water-loving and can easily diffuse through the water-permeable fenestrated endothelial cells and basement membrane. Large molecules and ions are unable to pass through the filtration barrier due to their size, charge, and hydrophobicity.

**Why Each Wrong Option is Incorrect:**

A. Filterable (Correct Answer) - This substance can easily pass through the glomerular membrane due to its size, charge, and hydrophilicity.
B. Non-filterable - This substance is large, charged, and hydrophobic, making it unable to pass through the filtration barrier.
C. Filterable - This substance has the same properties as the correct answer, but the question asks for the option that will pass easily.
D. Non-filterable - This substance is large, charged, and hydrophobic, which prevents it from passing through the filtration barrier.

**Clinical Pearl:** Understanding glomerular filtration is crucial for interpreting laboratory findings, such as blood urea nitrogen (BUN) and creatinine levels, in patients with kidney diseases. Increased BUN and creatinine levels indicate impaired filtration and reduced renal function.

**Correct Answer:** B. Non-filterable - This substance is large, charged, and hydrophobic, making it unable to pass through the filtration barrier.