下列试剂可作为基准物质直接配制标准溶液的是:
A. 优级氢氧化钠
B. 优级纯浓硫酸
C. 优级纯高锰酸钾
D. 优级纯重铬酸钾
They ____(live) in the suburb when she was only a child.
The football match ____(begin) at seven yesterday evening.
The students ____(play) basketball energetically on the playground right now.
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