[单选题]电气化铁路电力机车受电弓与接触点的移动距离D为线路外轨起道高度h的( )倍。
A. 1~2
B. 2~3
C. 3~4
D. 4~5

{{B}}The Future of the BBC{{/B}}
As a boy growing up in the 1930s in the Midlands, Norman Painting, the son of a railway-man, listened to a new radio service from the British Broadcasting Corporation. His mother hoped he would get a job as a manager at the mine, but listening to the voices from London talking about world affairs, culture and music gave him other ideas. "The radio opened a door to the world," says Mr. Painting, who went on to Oxford University on a scholarship and became an academic before later working for the BBC’s Radio 4 in its long-running soap, "The Archers".
Mr. Painting’s story helps to explain Britain’s devotion to what it calls "public-service broadcasting", and why the state has been standing by the BBC in the financing issue. The debate had raged for years over whether the BBC should still be publicly financed, especially by a license fee paid by all
A. The BBC’s terrestrial competitors
B. The Internet
C. The multi-channel services including digital channels, BBC3 and BBC4.
D. Newspapers and magazines.