Answer: B. Shrubland
Thornscrub ecosystem is found in between the Sonoran and Chihuahuan Deserts. It is typical shrubland. It consist of small trees like velvet mesquite and shrubs like Catlaw acacia, cactus which are common in Sonoran Desert. The Thornscrub shrubland exhibit distinct wet and dry seasons therefore, it possess growth of annual and perennial herbs. Therefore, the vegetation is determined by alternating dry and wet seasons.