If it is difficult to state definitely one or several ports, optional ports can be adopted.
假如难以明确写出一个或几个港口，就可以采用选择港这个办法。
Any of the eight ports can be configured as internal, external or optional.
任何端口均可配置为内部端口、外部端口或选配。
Lockable doors, desktop power, data ports, and a scalable power supply are optional features.
任选项包括可锁门，台式电源，数据端口，和可扩展电源。
Lockable doors, desktop power, data ports, and a scalable power supply are optional features.
任选项包括可锁门，台式电源，数据端口，和可扩展电源。
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