选出翻译得较好的一句。原句:连接亚欧两大洲的贸易通道丝绸之路全程达7000千米。它的历史可以追溯到公元前2世纪。 A. Silk Road, a trade thoroughfare linking the continents of Asia and Europe, is 7000-kilometer long. Its history can be dated back to the second century B.C.. B. The 7000-kilometer-long Silk Road is a trade thoroughfare linking the continents of Asia and Europe, which could date back to the second century B.C..