现有下列说法：  

①模型是对现实的简化，建模是为了更好地理解所开发的系统。  

②用例图定义了系统的功能需求，它是从系统的外部看系统功能，并不描述系统内部对功能的具体实现。  

③白盒测试仅与程序的内部结构有关，完全可以不考虑程序的功能要求。  

④软件技术复审是对用户和测试人员的一种质量保证活动。

错误的是(19)。

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  Remote administration types are an example of one kind of(71)malicious software, the Trojan horse, or more simply Trojan. The purpose of these programs isn't replication,(72)to penetrate and control. That masquerade as one thing when in fact they are something else, usually something destructive. There are a number of kinds of Trojans, including spybots, (73) report on the Web sites a computer user visits, and keybots or keyloggers, which record and report the user's keystrokes in order to discover passwords and other confidential information.

 RATS attempt to give a remote intruder administrative control of an infected computer. They work as(74)pairs. The server resides on the infected machine, while the client resides elsewhere, across the network, where it's available to a remote intruder. Using standard TCP/IP or UDP protocols, the client sends instructions to the server. The server does(75) it's told to do on the infected computer.

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现需要一个32M×8规格的存储器，现只有规格为1M×8的存储器芯片，则需要(49)个这样的存储器芯片。存储芯片的地址长度需要(50)位，主存储器的地址长度需要(51)位。

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