Final answer:
The Gulf Coastal Plains are considered the wettest ecoregion in Texas because they receive more rainfall, influenced by their proximity to the Gulf of Mexico and the moisture-laden marine currents and winds in the area.
Step-by-step explanation:
The Gulf Coastal Plains are considered to be the wettest of the Texas ecoregions primarily because B. The Gulf Coastal Plains receive more rainfall. The proximity to the Gulf of Mexico means that these plains are influenced by marine currents and winds that bring moisture into the region, leading to higher precipitation levels. In contrast, although the Piney Woods also receive significant rainfall, their topography and soil composition allow for better drainage, which means that the water does not accumulate as much as it does in the Gulf Coastal Plains.
Additionally, the Gulf Coastal Plains are characterized by wetlands and nearby shallow marine environments, which contribute to the overall moisture levels of the area. It is not necessarily due to the number of rivers and lakes (A), better drainage systems in the Piney Woods (C), or a higher elevation of the Gulf Coastal Plains (D), which is not the case. The region's climate, influenced by its geographic location near the Gulf, is the primary reason for its distinction as the wettest ecoregion.