设L={1,2,3,4,5,6,7,8,9,10,11,12}, 是偏序集,≤定义为:对于n1,n2∈L,n1≤n2当且仅当n1

设L={1,2,3,4,5,6,7,8,9,10,11,12}, 是偏序集,≤定义为:对于n1,n2∈L,n1≤n2当且仅当n1是n2的因子。问 是否为格?
【正确答案】:

不是格。哈斯图如下: