Which cloud type is described as a grey uniform layer that can produce drizzle?

The cloud type described as a grey uniform layer that can produce drizzle is indeed stratus. Stratus clouds typically appear as a flat, uniform layer that covers the sky, often resembling fog but at a higher altitude. These clouds are relatively low and can lead to overcast conditions, allowing for little variation in light. When stratus clouds produce precipitation, it is usually light, often manifesting as drizzle or mist rather than heavy rain.

In contrast, cumulus clouds are fluffy and white, often associated with fair weather, and do not generally produce significant precipitation. Cumulonimbus clouds are towering structures that signify thunderstorms and heavy rain due to their vertical growth and intensity. Nimbostratus clouds are also grey and can produce continuous rain, but they usually have a thicker appearance than stratus clouds and cover the sky more completely. Hence, the defining characteristics of stratus clouds make them the correct answer for this question regarding a uniformly grey layer that can yield drizzle.