(三) 甲城市至乙城市的高速公路即将贯通,经过市场调查与预测,甲、乙两城市之间的年日均班车客运量将达1680人次,由于两城市经济发展水平相当,往返客运量基本平衡。两城市运输距离为250千米。预期正式运行后车辆当日往返,平均车日行程500千米,运营车辆的单车额定载客量为50人。为了规范旅客运输市场经营秩序,以车辆工作率为80%、车辆实载率为70%的效率指标作为控制参营车辆数量的依据。 若按控制车辆效率指标计算,应投放50座客车______台才能实现甲、乙两城市之间班车客运运力与运量的基本平衡。
A. 17
B. 21
C. 25
D. 30
E. 60
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The Popularity of EnglishⅠ. Present status of EnglishA. English as a native/first languageB. English as a lingua franca: a language for communicationamong people whose(1)are differentC. Number of people speaking English as a first or a second language:— 320—380 million native speakers— 250—(2)million speakers of English as a secondLanguageⅡ. Reasons for the popular use of EnglishA. (3)reasons— the Pilgrim Fathers brought the language to America;— British settlers brought the language to Australia;— English was used as a means of control in(4)B. Economic reasons— spread of(5)— language of communication in the international business communityC. (6)in international travel— use of English in travel and tourism— signs in airports— language of announcement— language of(7)D. Information exchange— use of English in the academic world— language of(8)or journal articlesE. Popular culture— pop music on(9)— films from the USAⅢ. Questions to think aboutA. Status of English in the futureB. (10)of distinct varieties of English 9()
Question 6 is based on the following news. At the end of the news item, you will be given 10 seconds to answer the question. What is the main idea of the news item ()
A new government was formed after Sunday’s elections.
B. The new government intends to change the welfare system.
C. The Social Democratic Party founded the welfare system.
D. The Social Democratic Party was responsible for high unemployment.
用SQL语句完成下述要求。(1) 定义一个描述订单的客户号和对应订单明细中产品号关系的视图:客户产品(客户号,产品号)。(2)借助(1)所定义的视图,查询至少购买了01号客户购买的所有产品的客户号。SELECT客户号FROM客户产品 客户产品1WHERE (j) (SELECT*FROM客户产品 客户产品2WHERRE (k) (SELECT*FROM客户产品 客户产品3WHERRE (1) ));
带权图(权值非负,表示边连接的两顶点间的距离)的最短路径问题是找出从初始顶点到目标顶点之间的一条最短路径。假定从初始顶点到目标顶点之间存在路径,现有一种解决该问题的方法: ①设最短路径初始时仅包含初始顶点,令当前顶点u为初始顶点; ②选择离u最近且尚未在最短路径中的一个顶点v,加入到最短路径中,修改当前顶点u=v: ③重复步骤②,直到u是目标顶点时为止。 请问上述方法能否求得最短路径若该方法可行,请证明之;否则,请举例说明。