A.5% B.10% C.15% D.20%
A.一個(gè)月 B.三個(gè)月 C.六個(gè)月 D.十二個(gè)月
A.20m/s B.25m/s C.30m/s
A.3% B.5% C.10% D.15%
A.增大摩擦 B.擴(kuò)大頭輪 C.防止劃皮帶 D.潤(rùn)滑