n.改建
But, the prospect of rebuilding existing cable plants for high-speed bidirectional communications and extending cable until it matches the reach of copper is a difficult challenge. 但是，把現(xiàn)有的電纜線路設(shè)備改建成適合高速雙向通信延伸電纜直至與電話銅線相匹配是一個(gè)困難的挑戰(zhàn)。
