在喉口部位装有调节机构的文氏管称为调径文氏管，主要用于（）。
参考答案：精除尘
"Jack certainly has a low opinion of Susan." It can not be any worse than _______ of him. [ ]
A. hers
B. she does
C. her
D. she
我国的《公路沥青路面再生技术规范》建议水泥等活性填料一般不超过（）
A.1%
B.1.5%
C.2%
D.2.5%
