200 head cattle

200 head of cattle 200 head cattle "six head of cattle 10 head of cattle 为什么? five head of cattle 还是 five heads of cattle tow head of cattle 中的 head要加s吗 two head of cattle,head要加s吗?可是为什么ten head of cattle 又不用加s? a head of cattle 可以这样说吗?cattle 不是复数吗 两头牛英语怎么说?twenty heads of cattle 对么.还是twenty head of cattle Mr Smith bought twenty more head of cattle.这里的head 是否加s 英语表示一头牛：a head of cattle.而head也是头的意思, 5头牛five head of cattle ,head 不用复数啊?