焊接芯体时,应先将()去掉后才能焊接。
A、杂质
B、铁质
C、表皮
D、氧化层
参考答案:A, D
用所给词的适当形式填空
1. There ______ (be) a picture on the wall.
2. Are there ______(some) teachers in the classroom?
3. There ______(be) two pencils and a pen on the desk.
4. In the classroom, there ______ (be) ten students and a teacher.
5. There aren't any ______ (apple) in the box.
下列有利于大多数真菌产毒的条件是
A.相对湿度<70%
B.Aw<0.7
C.温度>30℃
D.厌氧
E.天然基质