题目

Beijing: The highly anticipated Beijing-Shanghai high-speed railway will begin operation next year, and is expected to cut travel time to four hours, railway officials said.     The high-speed railway between China's two most important metropolises was scheduled to open in 2012 but will now open one year ahead of time, said Zheng Jian, chief planner with the Ministry of Railways.     Wang Zhiguo, vice-minister of railways, said that it would be a four-hour journey from Beijing to Shanghai, and only three hours from Beijing to Nanjing, capital of East China's Jiangsu province.     A 已知直线x＋3y－7＝0，kx－y－2＝0与x轴、y轴围成的四边形有外接圆，则实数k的值是 [　　] A．－3 B．3 C．－6 D．6