boxcar的复数形式怎么写？

These goods are transported by boxcar, which can ensure absolute safety.这些货物都是用闷罐车运输的, 绝对安全....

n.货车车厢...

boxcar的音标：boxcar的英式发音音标为：['bɒkskɑ:(r)]boxcar的美式发音音标为：['bɑkskɑ(r)]...