B
The correct answer to this "security". It is a major factor in deciding if a centralized or decentralized environment is more appropriate. Example: In a centralized computing environment, you have a central server and workstations (often "dumb terminals") access applications, data, and everything else from that central servers. Therefore, the vast majority of your security resides on a centrally managed server. In a decentralized (or distributed) environment, you have a collection of PC`s each with their own operating systems to maintain, their own software to maintain, local data storage requiring protection and backup. You may also have PDA`s and "smart phones", data watches, USB devices of all types able to store data... the list gets longer all the time. It is entirely possible to reach a reasonable and acceptable level of security in a distributed environment. But doing so is significantly more difficult, requiring more effort, more money, and more time. The other answers are not correct because: scalability - A distributed computing environment is almost infinitely scalable. Much more so than a centralized environment. This is therefore a bad answer. heterogeneity - Having products and systems from multiple vendors in a distributed environment is significantly easier than in a centralized environment. This would not be a "challenge of distributed computing solutions" and so is not a good answer. usability - This is potentially a challenge in either environment, but whether or not this is a problem has very little to do with whether it is a centralized or distributed environment. Therefore, this would not be a good answer. Reference: Official ISC2 Guide page: 313-314 All in One Third Edition page: (unavailable at this time)