发动机VTEC的作用是（）。 ["解决低转速转矩","解决高转速动力","具有良好的怠速稳定性","以上答案全对"]
Which three statements accurately describe layer 2 Ethernet switches？（） ["Microsegmentation decreases the number of collisions on the network.","if a switch receives a frame for an unkown destination，it uses ARP to resolve the address.","Spanning Tree Protocol allows switches to automatically share vlan information.","In a properly functioning network with redundant switched paths，each swiched aegment will contain oneroot bridge with all its ports in the forwarding state.All other switches in that broadcast domain will haveonly one root port.","Establishing vlans increases the number of broadcast domains.","Switches that are configured with vlans make forwarding decisions based on both layer 2 and layer 3address information."]
在烧结矿宏观结构中，以（）的烧结矿强度最好。 ["粗孔蜂窝状结构","微孔海绵状结构","松散结构"]
无烟煤与其他煤相比，最突出的特点是（）。 ["固定碳高","挥发物少","灰份少","硫含量低"]
都市功能核心区的产业除了有现代服务业、金融服务，还包括以下哪些内容（）。
主体功能区的基本原理：根据不同区域的环境承载能力、现有开发强度和发展潜力，统筹谋划人口分布、经济布局、国土利用和城镇化格局，形成（）相协调的国土空间开发格局，并在不同区域形成主体功能，是区域发展的战略体现。
