美国石油学会(API)按照()进行基础油的分类。
A、粘度指数
B、碱性氮含量
C、硫含量
D、饱和烃含量
参考答案:A, C, D
More and more people are signing up for Yoga classes nowadays, ______ advantage of the health
and relaxation benefits.[ ]
A. taking
B. taken
C. having taken
D. having been taken
尖轨夹板与间隔铁之间必须保持一定的距离。