**Core Concept**
Glomerular filtration rate (GFR) is the rate at which fluid is filtered through the glomeruli of the kidneys. The GFR is influenced by several factors, including glomerular hydrostatic pressure, glomerular filtration barrier, and renal blood flow.

**Why the Correct Answer is Right**
An increase in renal blood flow leads to an increase in the number of glomeruli that are perfused, resulting in a higher GFR. This is because the glomeruli are the site of filtration, and an increase in blood flow increases the pressure within the glomeruli, allowing more fluid to be filtered. The increased renal blood flow also increases the amount of plasma that is available for filtration, further contributing to an increase in GFR. The renal autoregulation mechanisms, such as the tubuloglomerular feedback, help to maintain a relatively constant GFR despite changes in renal blood flow.

**Why Each Wrong Option is Incorrect**
**Option A:** Increased plasma oncotic pressure would actually decrease GFR, as it would decrease the amount of fluid that is filtered through the glomeruli.

**Option B:** Decreased glomerular hydrostatic pressure would also decrease GFR, as it would decrease the pressure within the glomeruli, making it more difficult for fluid to be filtered.

**Option D:** Increased tubular hydrostatic pressure would not directly affect GFR, as it is the pressure within the glomeruli, not the tubules, that determines the rate of filtration.

**Clinical Pearl / High-Yield Fact**
The renal autoregulation mechanisms help to maintain a relatively constant GFR despite changes in renal blood flow, which is essential for maintaining a stable fluid and electrolyte balance in the body.

**✓ Correct Answer: C. Increased renal blood flow. Increased renal blood flow leads to an increase in the number of glomeruli that are perfused, resulting in a higher GFR.**