烧结矿MgO含量提高，FeO含量（）
A、增高
B、降低
C、不变
D、无关
参考答案：A
用"are"或"is"填空。
1. There __________ three pencils and a pen in my pencil-box.
2. There __________ many kites in the sky.
3. There __________ a pen and two rulers on your desk.
4. There __________ a pencil-case in my bag.
5. There __________ two end tables near the bed.
6. There __________ some fish in a river.
断面法都有哪些种类？
