put computers to practical business use, but below the surface it is the heart of an(22) - the kernel - that provides the technical wizardry to juggle multiple programs, connect to networks and store(23).A traditional kernel provides all the functions for applications. The kernel(24) memory, I/O devices and parcels out processor time.The kernel also supports(25) and fault tolerance, which is the ability to recover automatically when parts of the system fail.
A. Databases
B. Applications
C. Drivers
D. Games
某县人口50万,约80%居民以河水为饮用水,该县设有一传染病科的综合医院。城市污水未经处理直接排入河水中。该县1986年1月-11月份伤寒发病人数达1063例,超过该县历史(1958-1985年)同期平均发病人数的6.9倍。初步调查,发现患者集中于河水排污口的下游地带。这一地区居民饮用河水者的伤寒发病率为6.5%,而饮用地下水者的伤寒发病为0.62%
根据上述资料,可初步判定伤寒患者突然大幅度增多的最可能原因是
A. 工业用水管线泄漏,工业废水污染了水源
B. 城市污水污染了水源
C. 供水过程中有被投毒的可能
D. 供水设施和净化消毒措施未能正常运转
E. 以上都不是