项羽和__________为争夺帝位，进行了四年的楚汉战争.
参考答案：刘邦
In the USA, he made a lot of friends ______ English well to make himself ______.
A．learn; understand
B．to learn; understood
C．learning; understand
D．learned; understood
安全切断阀也可由按键触动（）进行手动关闭。
A.手动复位机构
B.开启开关
C.解制机构
D.压缩弹簧
