下列哪一类型颈椎病发病率最高（）。
A.神经根型
B.脊髓型
C.椎动脉型
D.交感神经型
E.复合型
参考答案：A
下列选项中，对钒破坏催化剂叙述错误的是（）。
A、钒主要起脱氢作用
B、钒在氧环境下生成V2O5，熔融导致催化剂永久失活
C、钒在水蒸气气氛下，生成一种强酸VO（OH）3，破坏沸石晶体结构
D、钒与钠协同作用形成低熔点共熔物，减少活性中心，降低催化剂的热稳定性
Which of the following are problems in measuring unemployment （） Ⅰ. In order to be classified as unemployed, one must be looking for a job Ⅱ. People may be busy but their activities are outside the market labor force Ⅲ. Unemployed workers who are seeking work are included in the labor force along with employed workers
A. Ⅰ only.
B. Ⅱ only.
C. all of the above.
