What happens to an object requiring less motion to be seen in a clear blue sky compared to a partly cloudy sky?

When considering visibility in different sky conditions, the clarity and uniformity of a clear blue sky allows objects to stand out more against the background. In a clear blue sky, colors are more vibrant, and contrast is heightened, making it easier for the eye to detect motion or the presence of an object.

In contrast, a partly cloudy sky introduces variable lighting and texture, which can obscure visibility. Clouds can block light and change the perceived color, thus making an object harder to distinguish or requiring more effort for the observer to notice any motion against a less uniform backdrop.

Therefore, in a clear blue sky, an object requires less motion to be seen due to the enhanced visibility and contrast provided by the uniform background. This elucidation clarifies that "none of the above" accurately reflects that the other options do not effectively describe the visibility dynamics in different sky conditions.