nuclei air bubble

例句：

1. 1. The nucleus of thecell is where DNA is stored.
   细胞的核心是DNA存储的地方。
2. 2. The heart'snucleus controls its rhythm.
   心脏的核心控制着它的节律。
3. 3. Thenucleus of theplanet is the sun.
   行星的核心是太阳。