问题如下：
Which probability is not calculated from past data?
选项：
A.An empirical probability.
B.A priori probability.
C.A subjective probability.
解释：
C is correct.
An empirical probability uses past data to estimate the probability of an future event. A priori probability uses past data to deduce and summary the past events. They all use the past data. So, C is correct.
老师，请问C选项是什么意思？
