油类灭菌用
A.干热空气灭菌B.流通蒸气灭菌C.热压灭菌D.紫外线灭菌E.滤过除菌
参考答案:B
The singers ______ many concerts in the countryside since 2001.
A. hold B. held C. have held
对某水体的检测结果为,硝酸盐氮很高,未检到氨氮和亚硝酸盐氮。试对该水体的污染情况进行评价。