**Core Concept**
The Rosenbaum chart is an optotype chart used to measure visual acuity in patients. It consists of a series of high-contrast black letters on a white background, with each line containing a specific set of letters. The chart is designed to assess the sharpness of vision at a distance, making it a valuable tool in ophthalmology and optometry.

**Why the Correct Answer is Right**
The Rosenbaum chart is used to test visual acuity at a distance of 3 meters (10 feet). This distance is chosen because it allows for a consistent and standardized measurement of visual acuity, regardless of the patient's age or refractive error. The chart is typically hung at eye level, and the patient is asked to read the smallest line of letters that they can see clearly.

**Why Each Wrong Option is Incorrect**
* **Option A:** This is incorrect because the Snellen chart is typically used to test visual acuity at a distance of 6 meters (20 feet), not 3 meters.
* **Option B:** This is incorrect because the E chart is used to test visual acuity in patients with central field loss, not for general visual acuity assessment.
* **Option C:** This is incorrect because the Landolt chart is used to test visual acuity in patients with specific visual field defects, not for general visual acuity assessment.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the Rosenbaum chart should be hung at eye level and viewed from a distance of 3 meters to ensure accurate measurement of visual acuity. This standardized approach helps to minimize variability and ensure reliable results.

**Correct Answer: C. 3 meters.**