The eye of a hurricane is surrounded by dense black cumulonimbus clouds which are called the ____________.

The term that describes the dense black cumulonimbus clouds surrounding the eye of a hurricane is "wall cloud." This area is known as the eyewall, which contains the most intense winds and heavy rainfall of the hurricane. The wall cloud is characterized by its towering cumulonimbus structure, which typically features a well-defined, organized pattern of thunderstorms that encircle the calm eye at the center of the hurricane.

In contrast, the other terms mentioned do not specifically refer to the clouds surrounding the hurricane's eye. For instance, rain bands are long, narrow bands of showers and thunderstorms that spiral outward from the hurricane's eye and can extend far from the center. Cumulus clouds refer to a type of cloud that is not necessarily indicative of severe weather conditions like those found in a hurricane. Thunderhead generally describes the anvil-shaped clouds that form during thunderstorms but does not specifically pertain to the structure surrounding a hurricane's eye.

Therefore, recognizing the term "wall cloud" is crucial for understanding the unique and powerful structure of hurricanes, specifically the violent weather conditions present in the eyewall.