Scrambling of SONET signals is done to （）. [" prevent the leakage of external fiber emissions"," provide the optical network with the highest level of security possible"," assure an even distribution of 1's and 0's for extended transmitter life"," assure an adequate number of transitions for clock recovery at the receiver"," prevent the receiver from assuming AIS inadvertently when all 0's are received"]
鲁迅写小说最重要的贡献是（）上的突破。
What types of orders are exempt from using the IPCC Express Configuration and Ordering Tool? （） ["orders for coresident deployments ","orders for adding more seats ","orders for upgrading from standard ","orders with less than five seats ","all orders require using the IPCC Express Configuration and Ordering Tool&e"]
当前流行的程序设计方法是：（）和（）。
线路过长或过短的弊端是什么？
1993年末，北京作家打出了“（）”的旗号。于1994年初，在《北京文学》正式登台亮相。
