**Core Concept**
Albumin, a major plasma protein, is retained in the bloodstream due to the selective permeability of the glomerular filtration barrier. The glomerulus allows small solutes and water to pass through while restricting the passage of larger molecules like albumin.

**Why the Correct Answer is Right**
The glomerular filtration barrier consists of three layers: the endothelial cells, the glomerular basement membrane, and the podocytes. The podocytes have foot processes with slit pores that restrict the passage of albumin and other large molecules. The presence of negatively charged molecules like heparan sulfate in the glomerular basement membrane and podocytes also repels albumin, preventing its passage into the filtrate.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the selective permeability of the glomerular filtration barrier.
**Option B:** This option is not directly related to the restriction of albumin passage.
**Option C:** This option is incorrect as the presence of albumin in the urine is indicative of kidney damage or disease, not its normal passage through the glomerulus.

**Clinical Pearl / High-Yield Fact**
The glomerular filtration rate (GFR) is a critical indicator of kidney function, and a decrease in GFR can lead to the accumulation of waste products in the blood, including albumin.

**Correct Answer: D. The presence of negatively charged molecules like heparan sulfate in the glomerular basement membrane and podocytes.**