A.150 B.200 C.250 D.300
A.300 B.600 C.1000 D.500
A.長(zhǎng)度必須大于5米 B.長(zhǎng)度無(wú)要求 C.只能有1個(gè)對(duì)焊接頭 D.應(yīng)通長(zhǎng)