旋流式燃烧器分（）和（）两种。
参考答案：扰动式.轴向叶轮式
People living in the desert choose to keep their ancient lifestyles and customs,_______ people in cities
throw away their cultural traditions. [ ]
A. when
B. if
C. unless
D. while
炭黑聚集体表面有什么基团？炭黑的PH值与表面基团有什么关系？
