In which three network technologies is traffic shaping used to prevent and manage congestion？（） ["Asynchronous Transfer Mode （ATM）","data-link switching （DLSw）","Route Processor Redundancy （RPR）","Frame Relay （FR） ","Metro Ethernet","Multiprotocol Label Switching （MPLS）"]
科学计量法
长期卧床患者为避免体位性低血压，进行坐位耐力训练，一般从（）开始。 ["20°","30°","40°","60°","10°"]
秦始皇推行“书同文”字，作为官方通用文字的是（）。 ["金文","大篆","小篆","隶书"]
学前教育学
表层结构
