有关NaHCO₃和Na₂CO₃的性质，以下叙述错误的是 

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A．等质量的NaHCO₃和Na₂CO₃与足量盐酸反应，在相同条件下Na₂CO₃产生的CO₂体积大

B．等物质的量的两种盐与同浓度盐酸完全反应，所消耗盐酸的体积Na₂CO₃是NaHCO₃的两倍

C．将石灰水加入NaHCO₃溶液中不产生沉淀，加入Na₂CO₃溶液中产生白色沉淀

D．同物质的量浓度的两种溶液，Na₂CO₃溶液的pH大于NaHCO₃溶液

A certain clock marks every hour by striking a number of times equal to the hour and the time required for a stroke is exactly equal to the time interval between strokes. At 6:00 the time lapse between the beginning of the first stroke and the end of the last stroke is 22 seconds. At 12:00, how many seconds elapse between the beginning of the first stroke and the end of the last stroke ？（）

A.72

B.50

C.48

D.46

E.44