形容词可选择的; 随意的，任意的; 非强制的; 选修科目
1. 可选项：1) 个人用户证书基本项 可选项(Optional) 扩展项(Extend) 版本号 发证机构ID号 扩展序号序号 用户身份证ID 密钥用法签名算法 黑名单库分布点发证机构 政策URL 有效期限(包括签发日期和作废日期) 业务受理点ID 姓名 用户地址公
1. 可选择的；非强制的
If something is optional, you can choose whether or not you do it or have it.
e.g. A holiday isn't an optional extra. In this stressful, frantic world it's a must...
休假并非可有可无。在这个紧张而忙碌的世界，它是必不可少的。
e.g. Sex education is a sensitive area for some parents, and thus it should remain optional.
性教育对某些家长而言是个敏感领域，因此应该保持其非强制性。
1. Optional and decorative seasoning can be put on top of the steaming dish.
2. The accident happened during their visit to the Grand Canyon, an optional trip whose expenses were not included in the package price.
3. Since it was made optional nationwide in October 2003, the number of people undergoing the check has dropped tremendously.
4. Two optional sauces are mustard and Thai red chilli, which is really spicy.
5. But she said it is optional for publishers to submit articles to authorities for classification as they enjoy freedom of publication.
6. Shao said eBay EachNet charges sellers a fee for listing, a sales commission and an optional fee for making listings stand out from others.
7. Chinese food is like a luxury car with every conceivable optional extra thrown in.
8. It is divided into two kinds of accounts - lump sum deposit and withdrawal account, and time or saving optional deposit account.
9. The tourists were on their way back from visiting the Grand Canyon as part of an optional trip.
10. Fudan is the first university on the Chinese mainland to offer such a class as an optional course among its undergraduates.
adj
1. possible but not necessary
left to personal choice