4．设 $X \sim N\left(\mu_{1}, \sigma_{1}^{2}\right), Y \sim N\left(\mu_{2}, \sigma_{2}^{2}\right)$ ，这两个正态分布密度曲线如图所示．下列结论中正确的是
A. $P\left(Y \geq \mu_{2}\right) \geq P\left(Y \geq \mu_{1}\right)$
B. $P\left(X \leq \sigma_{2}\right) \leq P\left(X \leq \sigma_{1}\right)$
C. 对任意正数 $t, P(X \leq t) \geq P(Y \leq t)$
D. 对任意正数 $t, P(X \geq t) \geq P(Y \geq t)$
参考答案
C