以下语句实现的是面向对象的（）。 Public Class CustomerInfo Inherits PersonInfo ["继承","封装","接口","多态"]
Which device creates an OEO conversion？ （） [" amplifier"," attenuator"," regenerator"," light emitter"," optical switch"," optical receiver"," fiber-optic cable"]
晶胞
前照灯近光灯丝位于（） ["焦点上方","焦点后方","焦点","焦点下方"]
卵鞍
（）起，国家首次开展全面实施教师资格的认定工作，教师资格证书制度进入实际操作阶段。
