有多少个不同的四阶非同构阿贝尔群(一) 2 (乙) 3 (三) 4 (四) 5答案：(一)解释： 2 can be written as 2 power 2. Number of partitioning of 2 = no. of non isomorphic abelian groups 2 can be partitioned as {(2),(1,1)} 这个问题的测验