控制柴油产品硫含量可通过改变（）手段来进行。
A、脱金属催化剂活性
B、脱硫催化剂活性
C、脱氮催化剂活性
D、保护剂活性
参考答案：B
Kate _________ in America for many years, but she’d never regretted her decision to return to her motherland.
A．worked
B．was working
C．has worked
D．had worked
什么是Ⅲ类计量装置？
