问题补充：
THE 2,298-kiIometer Beijing-Guangzhou High-speed Railway 【小题1】 (official) opened to passengers on December 26，. It is the world’s longest high-speed rail route. The 【小题2】 (design)speed of the track is 350 km^, though speeds during the initial period of operation will be limited to about 300 km/h. The new route cuts the travel time between Beijing and Guangzhou【小题3】almost two thirds, from 22 hours to roughly eight hours .On December 1, ，not long before the opening of the Beijing-Guangzhou High-speed Railway, the Harbin-Dalian High-speed Railway, 【小题4】 first high-speed line ever to cross land that lies frozen for almost half a year, began operations, 【小题5】 allows passengers to appreciate the view off the coast from Dalian in the morning, 【小题6】 the winter snowscape of frosty Harbin in the afternoon .At present the total 【小题7】 (long) of high-speed lines in China 【小题8】(reach)9,349 km. With four main lines 【小题9】 (run) east-west and four north-south, the country’s high-speed train network is the world’s largest. China plans to expand 【小题10】_ high-speed railway network to 50，000 km by , to cover almost all large and medium-sized cities.officially
答案：
(答案→)officially
解析：
【小题1】修饰动词opened用副词： officially正式地
【小题2】考查过去分词做定语：designed修饰speed，设计的速度
【小题3】考查介词：新路线可以把北京和广东的时间较少三分之二，表示差值：用 by
【小题4】考查序数词：第一个高铁线路：the first high-speed line
【小题5】考查定语从句：which引导定语从句，指前面的句子，在定语从句中which做主语，这使得乘客可以欣赏沿海的风景。
【小题6】沿海的风景和哈尔滨的雪景是并列的：and
【小题7】考查名词：铁路的总长度，用名词：length
【小题8】考查时态：时间是At present 用现在完成时：has reached
【小题9】考查with复合结构：four main lines 和run是主动关系：running
【小题10】中国计划扩大高铁网络系统到50，000公里。Its指代China’s.
