A.接入網(wǎng) B.短途網(wǎng) C.長途網(wǎng) D.傳輸網(wǎng)
A.接入網(wǎng) B.短途網(wǎng) C.中繼網(wǎng) D.傳輸網(wǎng)
A.4900km B.5900km C.6900km D.7900km