nucleus的复数形式是什么

　　例句：

　　A neutron is simply a neutral particle in the nucleus of an atom.

　　中子就是原子核里不带电的粒子。

　　The nucleus is the information center of cell.

　　细胞核是细胞的信息中枢。

　　Many people believe that the family is the nucleus of the community.

　　许多人认为家庭是社会的核心。