题目内容：

—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

优质解答

考察名词.由于how many后面接复数可数名词,很容易错选B或D.事实上,head指“(表示农场或牧群的数目)头”时,单复数同形；cattle本身就表示复数概念.因此答案为A.