**Core Concept**
Filtration barriers, such as the glomerular basement membrane in the kidneys, have pores that regulate the passage of molecules and particles. The size of these pores determines the filtration cutoff, which is crucial for maintaining fluid and electrolyte balance.

**Why the Correct Answer is Right**
The glomerular basement membrane has pores with a diameter of approximately 70-80 angstroms (Å), allowing small molecules like water, ions, and glucose to pass through while restricting larger molecules like proteins and blood cells. This selective permeability is essential for proper kidney function. The glomerular filtration rate (GFR) is influenced by the surface area of the glomerular capillaries, the filtration pressure, and the size of the pores.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not provide a relevant size range for the pores of filtration barriers.
**Option B:** This option is incorrect because it suggests a pore size that is too large, which would compromise the barrier's ability to filter waste and excess substances.
**Option C:** This option is incorrect because it suggests a pore size that is too small, which would significantly reduce the glomerular filtration rate and lead to fluid buildup.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that the glomerular filtration barrier is a dynamic structure that can be affected by various factors, including hypertension, diabetes, and kidney disease.

**Correct Answer:** C. 70-80 angstroms (Å)