C类粉煤灰是由褐煤或次烟煤锻烧收集的粉煤灰,其氧化钙含量一般大于()。
A、10%
B、20%
C、30%
D、40%
参考答案:B
用所给词的适当形式填空。
1. Mr. Dean ________ (drive) his new car on the street.
2. Many students enjoy ________(listen) to the music after school.
3. Most of us don't agree with ________(he).
4. Let's ________(drink) some orange juice.
5. There ________ ( not be) any water in the bowl.
抽水试验层(段)的孔径一般不应小于()mm,下过滤器时,过滤管的直径不应小于()mm。