You took an optional course this semester, didn't you?
你这学期选了一门选修课，是吗？
If you see humor as an optional form of entertainment, you're missing some of its biggest benefits: humor makes average-looking people look cute and uninteresting people seem entertaining.
如果你认为幽默只是一种可有可无的娱乐形式，那你就忽略了幽默最大的好处：幽默能让长相平平的人看起来更可爱，也能让呆板无趣的人看起来更有趣。
But if the string is an address or optional field, you may have megabytes of zeroes on disk.
但如果字符串是一个地址或可选的字段，那么磁盘上可能会有成兆字节的零。
Finally, you can enter an optional description and category.
最后，您可以填写可选的描述和类别项。
The domain is optional, only required if you need to perform cross-domain authentication.
域是可选的，只有在您需要执行跨域的验证时才需要。
You can even make fields optional or required.
甚至还能将字段设置为可选或必需的。
Download all required parts — and any optional parts that you choose — to the same temporary directory.
将所有所需的部分——以及您选择的所有可选部分——下载到同一个临时目录下。
All of the additional parameters are optional so you specify only as much information as you want.
所有其它参数都是可选的，因此您只指定您想要的信息便可。
You can list the time you spend shopping for work clothes, or time you spend going out for business dinners, or time you spend doing "optional" training.
你能列出你挑选和购买职业装所花的时间，或者你用于参加商务晚宴的时间，或者你用于做“可选的”旅行的时间。
At first, the logic behind this sounds reasonable: If you change this data element from optional to required, you essentially duplicate error processing that occurs elsewhere in the system.
首先，整个过程背后的逻辑是合理的：如果您将这项数据元素从可选改为必需，那么您基本上就是复制了系统中其他地方所使用的错误处理过程。
User id and password are optional, and you can provide them at the time of connection.
用户ID和密码是可选的，您可以在连接的时候提供它们。
The others are optional, depending on which products you want extensions for.
其他插件都是可选的，具体取决于您想要哪个产品的插件。
Note: actually listening to music through your headphones is optional - nobody knows but you.
注意：戴上耳机之后，听不听音乐是由你自己选择的——反正只有你自己知道。
You also send an optional message to the peer to indicate that you're available.
您还可以发送一个可选信息给对方，告诉对方您已在线了。
You can specify an optional storage for the metrics as well.
还可以为指标指定可选的存储。
The TIO integration is optional, but powerful if you are a TIO customer.
TIO集成是一个可选项，但如果您是一位 TIO客户，那么它的功能是非常强大的。
Recall from the XSD file that you also generated optional XML data.
回忆一下同时生成可选XML数据的XSD文件。
You can set the optional skip to true if the user can skip the task.
如果用户可以跳过这个任务，您可以将skip选项设为true。
You might have an optional subdirectory called lib as well.
还可能有一个可选的子目录，名为lib。
This parameter is optional: if you don't specify extra keywords, all is assumed.
该参数是可选的：如果您不指定额外的关键字，假定使用all。
It also determines if you have the optional Perl modules that support features such as graphical charts and reports.
它还会确认您是否拥有支持曲线图和报表等特性的可选perl模块。
Since DB2 9.5 you can add the optional clause REJECT INVALID VALUES to your XML index definition.
从DB 2 9.5往后，您就可以向xml索引定义添加可选的REJECTINVALIDvalues子句。
Delete optional Windows components that you don't use.
删除您不使用的可选Windows组件。
Remove optional Windows components that you don't use.
删除您不使用的可选Windows组件。
ActionScript lets you have optional parameters, but they must have default values to use.
ActionScript允许有可选参数，但必须有可用的缺省值。
You can pass an optional data object and callback function if you need them.
如果需要的话，您还可以传递一个可选的数据对象和回调函数。
Some functions contain optional input parameters, which you can add or remove as needed.
一些函数包含可选的输入参数，可以根据需要添加或删除它们。
The submission rule is optional; you need it only if you want to submit just the data instance instead of the entire form.
提交规则是可选的；只有在希望提交数据实例而不是整个表单的情况下，才需要提交规则。
After you have populated all mandatory and any optional fields, click OK.
当您填充所有强制性和任何非强制性字段后，点击ok。
If you have optional attributes in an element or default values for attributes, the wizard may omit them depending on what is in your XML instance.
如果元素中有可选属性，或属性有缺省值，向导可能会根据XML实例中的情况忽略这些内容。
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