A. are made of bronze,brass,or soft alloy metals B. should be painted red in order to identify hose lengths C. are specially hardened to prevent crushing D. should be greased frequently
A. 稽文甫 B. 张予林 C. 张彬 D. 肖红
A. 一块斜铁配一块平铁 B. 两块斜铁配一块平铁 C. 一块斜铁配两块平铁 D. 两块斜铁配四块平铁
A. 正确 B. 错误