cattle是可数名词吗?如果是,那为什么要用计量词（a head of cattle）

cattle是可数名词吗?如果是,那为什么要用计量词（a head of cattle） two head of cattle,head要加s吗?可是为什么ten head of cattle 又不用加s? 10 head of cattle 为什么? tow head of cattle 中的 head要加s吗 a head of cattle 可以这样说吗?cattle 不是复数吗 200 head of cattle "six head of cattle cattle和police是可数还是不可数名词? 为什么panda是个体名词而cattle是集合名词? five head of cattle 还是 five heads of cattle 两个句子对错~是They sold twenty head of cattle this week.还是They sol pig Cattle复数是