Which of the following prescriptions is converted to a single vision intermediate prescription?

To determine which prescription can be converted to a single vision intermediate prescription, it's essential to evaluate the characteristics of each prescription.

A single vision prescription typically contains either a spherical or a cylindrical component intended for one specific distance. In the context of intermediate vision, which is typically defined as a distance of approximately 40 to 70 cm, a prescription would need to be suitable for that range.

The selected prescription features a combination of a negative sphere and a negative cylinder (indicated by the "x" axis). This prescription designates a correction for myopia, which is required for clear vision at that intermediate distance. A significant factor here is that both the sphere and cylinder are negative, suggesting that it is designed for clarity at that distance rather than being solely for distance or near vision.

When evaluating the other choices, one may find that they do not fit the criteria for conversion into a single vision intermediate prescription. Prescriptions that have positive spherical components, especially if accompanied by a significant positive cylinder, are typically designed for hyperopia corrections aimed at distance rather than intermediate vision.

Thus, the prescription that converts effectively to a single vision intermediate is one that primarily accommodates the visual needs at that specific range, aligning perfectly with option C.