单选题 Geological evidence suggests that wildfires do not occur as ______ as they used to in the Victorian Basin.

【正确答案】 C

【答案解析】除去as…as…部分，that引导的从句可以简化为wildfires do not occur______。空格处应填入修饰动词occur的副词，因此(C)选项frequently是正确答案。