kernel seed coat colour

例句：

1. 1.The kernel of the problem is that it's not sustainable.
   问题的核心是它不可持续。
2. 2.The kernel of this new policy is its focus on environmental protection.
   这项新政策的重点是环境保护。
3. 3. The kernel of the cake is made from wheat flour and eggs.
   蛋糕的主要成分是由小麦面粉和鸡蛋制成的。