The Winter Olympics are held（ ）选every four year 还是every fourth year?理由是什么?

every four year

every four year
every fourth year这种说法本身就是错误的。

给一楼补充点。。
The winter olympics are held every four years.
翻译：冬季奥林匹克运动会每隔四年举行一次。
The winter olympics are held every fourth year.
翻译：冬季奥林匹克运动会在每三年后的第四年举行一次（有点绕口）
every +基数+ years 强调的是每隔几年
every + 序数+ year 强调的是第几年

选every four year ,---------------每4年

选every fourth year,前面一个表达是错误的,应该是every four years.
every fourth year =every four years
every 与基数词、序数词、other 和few 连用,表示时间或空间的间隔,意为“每……；每隔……”.如：
He comes here every three days (every third day).他每三天(每隔两天)来这儿一次.
You'd better plant a tree every five meters(every fifth meter).你最好每(隔)5米种一棵树.(树的空间忽略不计)
Write on every other line.隔行写.
every other day 每隔一天
every few days 每隔几天(注意“few”前没有“a”)