根据附图依次选出聚光灯、光束灯、散光灯的符号（）。 A）是光束灯的符号。 B）是聚光灯的符号。 C）是散光灯的符号。 D）是幻灯的符号。 E）是回光灯的符号。
You are deploying two core switches， one in each building， 50 km away from each other. The cross-connection between them will be a Layer 2 2-gigabit EtherChannel with an 802.1Q trunk. You configured it correctly but the link does not come up. The port is in the "admin up" state， and the line protocol is in the "down" state. The fiber link is OK. What would be the most likely reason for the link not to come up？（） The switches are not the same model.。 You are not using the correct SFP.。 You are not using correct optical media converters.。 Configuration should be modified， because the distance is longer.。
为什么说班级是学生成长的重要环境。
what is ABR？
为防止绞接顶梁梁头扎破金属网，可利用旧木料在（）处垫好。 梁头。 网头。 梁尾。 梁窝。
（）在农产品物流领域主要用于农产品运输车辆的跟踪与三维导航。
