**Core Concept**
Pre-eclampsia is a pregnancy complication characterized by high blood pressure and damage to organs such as the kidneys and liver. A key diagnostic criterion is the presence of significant proteinuria, which can be quantified using the protein/creatinine ratio.

**Why the Correct Answer is Right**
The protein/creatinine ratio is a useful screening tool for detecting pre-eclampsia in pregnant women. A ratio of 0.3 or greater is generally considered indicative of significant proteinuria, which is a hallmark of pre-eclampsia. This is because the kidneys are damaged, leading to the leakage of large amounts of albumin into the urine. The protein/creatinine ratio takes into account the concentration of both protein and creatinine in the urine, allowing for a more accurate assessment of proteinuria than a simple urine dipstick test.

**Why Each Wrong Option is Incorrect**
* **Option A:** A ratio of 0.1 is not considered significant proteinuria and would not suggest the development of pre-eclampsia.
* **Option B:** A ratio of 0.5 or greater is generally considered indicative of significant proteinuria, but the specific value that suggests development of pre-eclampsia can vary depending on the institution and clinical context.
* **Option D:** A ratio of 0.1 is not considered significant proteinuria and would not suggest the development of pre-eclampsia.

**Clinical Pearl / High-Yield Fact**
Remember that the protein/creatinine ratio is a screening tool and not a diagnostic test. A high ratio may indicate pre-eclampsia, but further evaluation and confirmation by a healthcare provider are necessary to make a definitive diagnosis.

**Correct Answer:** C.