A.交叉兩桿 B.交叉四桿 C.平行兩桿 D.平行四桿
A.30萬km B.60萬km C.120萬km D.240萬km
A.金屬節(jié)點(diǎn) B.關(guān)節(jié)軸承 C.金屬鋼套 D.橡膠節(jié)點(diǎn)