使用电子邮件客户端从服务器下载邮件，能实现邮件的移动、删除等操作在客户端和邮箱上更新同步，所使用的电子邮件接收协议是（ ）。
电子邮件协议通常包括SMTP和POP3，其中SMTP是电子邮件发送协议，POP3是电子邮件接收协议。
MIME是多用途互联网邮件扩展，它是一个互联网标准，扩展了电子邮件标准，使其能够支持：非ASCII字符文本；非文本格式附件（二进制、声音、图像等）；由多部分组成的消息体；包含非ASCII字符的头信息（Header information）。
IMAP和POP3的区别是：POP3协议允许电子邮件客户端下载服务器上的邮件，但是在客户端的操作（如移动邮件、标记已读等），不会反馈到服务器上，比如通过客户端收取了邮箱中的3封邮件并移动到其他文件夹，邮箱服务器上的这些邮件是没有同时被移动的。而IMIAP客户端的操作都会反馈到服务器上，对邮件进行的操作，服务器上的邮件也会做相应的动作。本题描述的是C项。
Unified Modeling Language（UML） is a widely used method of visualizing and documenting an information system. The UML can be used to develop（ 71 ）, in which an object represents a person, place, event, or transaction that is significant to the information system. Systems analysts define an object's attributes during the（ 72 ）. An object also has（ 73 ）which are tasks or functions that the object performs when it receives a message, or command, to do so. A（n）（ 74 ）is a group of similar objects. If objects are similar to nouns, attributes are similar to adjectives that describe the characteristics of an object. Objects can have a specific attribute called a（n）（ 75 ）, which of an object is an adjective that describes the object's current status. All objects within a class share common attributes and methods, so a class is like a blueprint, or template for all the objects within the class.
Unified Modeling Language（UML） is a widely used method of visualizing and documenting an information system. The UML can be used to develop（ 71 ）, in which an object represents a person, place, event, or transaction that is significant to the information system. Systems analysts define an object's attributes during the（ 72 ）. An object also has（ 73 ）which are tasks or functions that the object performs when it receives a message, or command, to do so. A（n）（ 74 ）is a group of similar objects. If objects are similar to nouns, attributes are similar to adjectives that describe the characteristics of an object. Objects can have a specific attribute called a（n）（ 75 ）, which of an object is an adjective that describes the object's current status. All objects within a class share common attributes and methods, so a class is like a blueprint, or template for all the objects within the class.
Unified Modeling Language（UML） is a widely used method of visualizing and documenting an information system. The UML can be used to develop（ 71 ）, in which an object represents a person, place, event, or transaction that is significant to the information system. Systems analysts define an object's attributes during the（ 72 ）. An object also has（ 73 ）which are tasks or functions that the object performs when it receives a message, or command, to do so. A（n）（ 74 ）is a group of similar objects. If objects are similar to nouns, attributes are similar to adjectives that describe the characteristics of an object. Objects can have a specific attribute called a（n）（ 75 ）, which of an object is an adjective that describes the object's current status. All objects within a class share common attributes and methods, so a class is like a blueprint, or template for all the objects within the class.
Unified Modeling Language（UML） is a widely used method of visualizing and documenting an information system. The UML can be used to develop（ 71 ）, in which an object represents a person, place, event, or transaction that is significant to the information system. Systems analysts define an object's attributes during the（ 72 ）. An object also has（ 73 ）which are tasks or functions that the object performs when it receives a message, or command, to do so. A（n）（ 74 ）is a group of similar objects. If objects are similar to nouns, attributes are similar to adjectives that describe the characteristics of an object. Objects can have a specific attribute called a（n）（ 75 ）, which of an object is an adjective that describes the object's current status. All objects within a class share common attributes and methods, so a class is like a blueprint, or template for all the objects within the class.
Unified Modeling Language（UML） is a widely used method of visualizing and documenting an information system. The UML can be used to develop（ 71 ）, in which an object represents a person, place, event, or transaction that is significant to the information system. Systems analysts define an object's attributes during the（ 72 ）. An object also has（ 73 ）which are tasks or functions that the object performs when it receives a message, or command, to do so. A（n）（ 74 ）is a group of similar objects. If objects are similar to nouns, attributes are similar to adjectives that describe the characteristics of an object. Objects can have a specific attribute called a（n）（ 75 ）, which of an object is an adjective that describes the object's current status. All objects within a class share common attributes and methods, so a class is like a blueprint, or template for all the objects within the class.
为了控制IP报文在网络中无限转发，在IPv4数据报首部中设置了（ ）字段。
在Linux系统中，DNS配置文件的（ ）参数，用于确定DNS服务器地址。
用户在登录FTP服务器的过程中，建立TCP连接时使用的默认端口号是（ ）。
使用电子邮件客户端从服务器下载邮件，能实现邮件的移动、删除等操作在客户端和邮箱上更新同步，所使用的电子邮件接收协议是（ ）。
Cookie为客户端持久保持数据提供了方便，但也存在一定的弊端。下列选项中，不属于Cookie弊端的是（ ）。
