---When were you born? -I was born a cold winter morning in 1996A on B. in C. at

问题补充：

---When were you born?

---I was born a cold winter morning in 1996.

A on B. in C. at

答案：

解析：介词的用法。在具体的一天的某个时间段，如果有形容词修饰，应该用介词on。