认证按对象可分为哪二大类？按其性质又可成哪两大类？
参考答案：
认证按对象可分为产品认证和管理体系认证。按其性质又可分为强制性认证和自愿性认证。
转化炉的反应温度升高，出口工艺气中的甲烷含量将（）。
A、升高
B、降低
C、不变
D、不一定
根据句意补全单词中所缺字母，使补全后的句子通顺、合理。
l.—What colour is Ann's skirt?
—It's r____d.
2.We often play g____mes after school.
3.Put your r____ler and your pen in the pencil-box.
4.My parents work f____ ve days a week.
5.There are a lot of cars and buses in the str____t.
6.Don't open the wind____ . It's cold outside.
