【正确答案】 B

【答案解析】[听力原文]29-30 Forensic experts yesterday began searching for clues in a bomb-shattered carriage lying 500 yards into one of the oldest and deepest Tube lines. The pace was slow and the approach delicate because the bodies of as many as 20 victims of the Piccadilly Line bomb near King's Cross were still trapped in the wreckage. After engineers declared the tunnel structurally safe, the aim was to remove the dead and start a fingertip examination. If the experts are lucky, they will find chemical traces, tiny scraps of bomb casing or detonation and timing devices. The carriage may be removed from the tunnel to allow better access but that could involve dismantling it, which could take many days. Similar searches started 100 yards into a tunnel near Liverpool Street station, where another of the bombs went off, and outside Edgware Road. Bodies were recovered and it was hoped that the two carriages could be removed. 根据新闻，法医专家最需要搜寻的是爆炸的线索或者证据。而所给的选项好像都不是，又好像都是。首先要听新闻的头一句话Forensic experts yesterday began searching for clues，然后，就是寻找炸药的化学成分和弹壳等，再就是指纹。

【正确答案】 D

【答案解析】由于新闻里没有具体提到需要多少天，只是说会花很多天，所以，答案是D。