nucleus的復數形式是什么

　　例句：

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

　　中子就是原子核里不帶電的粒子。

　　The nucleus is the information center of cell.

　　細胞核是細胞的信息中樞。

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

　　許多人認為家庭是社會的核心。