The correct answer is c. regional.
The trade winds are a system of prevailing winds that blow from the east to the west near the equator. These winds can carry aerosol clouds and smog from one island to another, which can have a negative impact on the environment. For example, the trade winds can carry volcanic ash from an eruption on one island to another, which can cause respiratory problems for people living on the affected islands. Additionally, the trade winds can carry smog from one island to another, which can reduce air quality and visibility.
The effects of the trade winds carrying aerosol clouds and smog to other islands are experienced at the regional level because they impact multiple islands. The effects are not limited to the island where the volcanic eruption occurs, nor are they limited to a single individual. The effects are also not global, as they do not impact the entire planet.