Which type of middle cloud is known for providing some sunlight visibility?

The correct choice is altostratus. This type of middle cloud is characterized by its uniform, gray or blue-gray appearance that typically covers the entire sky, allowing some sunlight to filter through. Altostratus clouds are often associated with a stable atmosphere and can produce light precipitation, but they do not completely block sunlight, making them distinct in their ability to still allow visibility.

Stratus clouds, on the other hand, are low-level clouds that also cover the sky, but they tend to produce thicker coverage that may obscure sunlight more than altostratus. Nimbostratus clouds are usually darker and are associated with continuous, steady precipitation, which significantly limits sunlight visibility. Cumulus clouds, while they can form at mid-levels, are often characterized by their puffy, cotton-like appearance and are typically not classified as middle clouds; they usually do not provide the same level of sunlight visibility as altostratus.