用an，例如：

1. She cracked an egg into the pan.她往锅里打了一个鸡蛋。

2.Crack an egg and separate the yolk immediately.打一个鸡蛋，然后立刻将蛋黄分离出来。3.Add an egg yolk to make the mixture bind.加个蛋黄使混合料凝结在一起。4.Suppose someone gave you an egg and asked you to describe exactly what was inside.假设有人给了你一枚鸡蛋并要你准确描述鸡蛋里面有什么。