题目

  John Snow was a famous doctor in London who ____________61（护理）Queen Victoria as her personal          ___________ 62（医生）. He thought about helping ordinary people ______________63（被暴露）to cholera. Though the cause and the ___________ 64（治疗）of it were unknown, he wanted to face the          ___  65（挑战）and solve the problem. When another outbreak hit London in 1894, and the disease spread quickly through poor n_____________66 , he began to gather information. He m _________ 67 on a map where all the dead people had lived and he  MOH和ROH两种一元碱的溶液分别加水稀释时， pH变化。如右图所示。下列叙述中正确的是                                             A．ROH是一种弱碱           B．在x点，c(M＋) ＝ c(R＋) C．在x点， MOH完全电离     D．稀释前，c(ROH) ＝10 c(MOH)