nipple for auxiliary steam connecting

例句：

1. 1. The baby'snipple is sore from nursing.
   婴儿的乳头因为哺乳而变得疼痛。
2. 2.The nipple of the cow hasa unique shape.
   牛的乳头形状独特。
3. 3.The nipple of the cow issoft and warm.
   牛的乳头柔软且温暖。