配制标准缓冲液与溶解供试品的水,应是新沸过的冷水,其pH应为
A.3.5~5.5B.4.0~6.5C.5.5~7.0D.5.5~8.0E.6.0~8.0
参考答案:C
In school,there are 30 classes.[ ]
A.we
B.our
C.us
D.were
什么是非常规水资源?