the heads of中的head为什么要加s

the heads of中的head为什么要加s 名词所有格,_____are grazing in the fields.A.ten heads of cattleB.ten head of cattleC.ten heads of cattlesD.ten head of cattles为什么? five head of cattle 还是 five heads of cattlefive head of cattle中head 加不加s? 是5 head of 还是 5 heads of 200 head of cattle是还是200 heads of 200 head cattle ,200 head of cattle ,200 head cattles,200 heads of cattle? at the heads of 是什么意思 heads-of-house是什么意思?原文为：Data for the test were gathered from 506 interviews with female heads-of-house living in the trading area of metropolitan Oakland. the head of the join together at the side of heads when I read the telegram, I just couldn't make heads or tails out of it.head or tail是啥意思, 整句话是啥意思 at the head of the head of 关于cattle 这个单词是“three heads of cattle”还是three head of cattle? heads of cabbage是什么意思?heads of呢? the head of the head of movie company是什么意思? —How many ____ does your uncle have on his farm? —Twenty, I think. A. head of cattle B. heads of cattle C. head of cattles D. heads of cattles the head of 的意思