$A.$ $P(A \mid B)=P(\bar{A} \mid B)$. $B.$ $P(A \mid B) \neq P(\bar{A} \mid B)$. $C.$ $P(A B)=P(A) P(B)$. $D.$ $P(A B) \neq P(A) P(B)$.

C

#### 解析：

$$\frac{P\{A B\}}{P\{A\}}=\frac{P\{\bar{A} B\}}{P\{\bar{A}\}}=\frac{P\{B\}-P\{A B\}}{1-P\{A\}},$$