machinery单数还是复数

　　The factory's machinery pounded away day and night.

　　工厂的机器昼夜轰隆作响。

　　The group can't get credit to buy farming machinery.

　　该集团无法以赊购方式购买农业机械。

　　Machinery was often unprotected and accidents were frequent.

　　机器常裸露着，因此事故频仍。

　　He had interfaced all this machinery with a master computer.

　　他已将这整台机器与一台主控计算机连接起来。

　　There are new tractors and new ploughs in the machinery lot.

　　机器设备场里有新拖拉机和新耕犁。