Which type of environment is most conducive to sudden oak death?

The correct answer highlights that cool and wet forests create an environment particularly favorable for the pathogen responsible for sudden oak death, which is caused by the Phytophthora ramorum organism. This pathogen thrives in conditions where there is high moisture—typically found in cooler climates with regular rainfall. Such environments facilitate the spread of spores and the infection of susceptible oak trees, as the wet conditions allow for better survival and reproduction of the pathogen.

In cooler, wetter forests, the organic matter and leaf litter provide a suitable habitat for Phytophthora ramorum, boosting its lifecycle and infectivity. The combination of moisture-laden air and shade also helps in maintaining the damp conditions necessary for the pathogen to flourish and spread among the forest ecosystem.

In contrast, the other environments listed do not offer the same level of suitability for the pathogen. For instance, dry and hot forests would not provide the necessary humidity levels needed for the pathogen's growth, while urban areas with high pollution may exhibit less susceptible tree populations or disturbing ecological balance that limits disease spread. Sandy soil environments typically have quick drainage, which would also not support the consistent moisture required for the pathogen to thrive. Thus, it is the cool and wet forests that provide the ideal conditions for the occurrence of sudden oak death