The university has launched a research center to develop new ways of ______ bacteria which
A. regulating
B. halting
C. interrupting
D. combating
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Not having a good command of English can be a serious ______ preventing you from achieving
A. obstacle
B. fault
C. offense
D. distress
当物质的基本单元为下列化学式时,它们分别与NaOH溶液反应的产物如括号内所示。与NaOH溶液反应时的物质的量之比为1:3的物质是()。
A. H3PO4(Na2HPO4)
B. NaHC2O4·H2C2O4(Na2C2O4)
C. H2C8H4O4(Na2C8H4O
滴定管的读数误差常有±0.02 mL,若要求相对误差不大于0.1%,为此滴定管消耗标准溶液的体积必须不小于()。
A. 10 Ml
B. 20 mL
C. 30 mL
D. 25 mL
用法扬司法测定C1-寸,用曙红(Ka=10-2)为指示剂,分析结果会()。
A. 偏高
B. 偏低
C. 准确
D. 不能判断