设随机变量<img src="https://static.zxtiku.com/wangke/imgs/topic/9ddd8feb75c81353185faec94a8b7091.jpg"/>，对给定的<img src="https://static.zxtiku.com/wangke/imgs/topic/0809fce0078791d4e65b1c6a440ac0d6.jpg"/>，数<img src="https://static.zxtiku.com/wangke/imgs/topic/e67658adb1c7a4c97254aa7b2b267d2c.jpg"/>满足<img src="https://static.zxtiku.com/wangke/imgs/topic/5704a66b0a1fcc8a18f9ec739bf7d0f5.jpg"/>。若<img src="https://static.zxtiku.com/wangke/imgs/topic/9824c214080a573375961bd589fcfa4a.jpg"/>，则<img src="https://static.zxtiku.com/wangke/imgs/topic/5f4416975701debd1779850877ce0e35.jpg"/>等于（）<br/> A、<img src="https://static.zxtiku.com/wangke/imgs/topic/dc61604308bf6872eecc8fffda982024.jpg"/><br/> B、<img src="https://static.zxtiku.com/wangke/imgs/topic/1cafbdd50a25c32010b912490fc5ad68.jpg"/><br/> C、<img src="https://static.zxtiku.com/wangke/imgs/topic/70de2baa10428b08f64c4c20231d4c01.jpg"/><br/> D、<img src="https://static.zxtiku.com/wangke/imgs/topic/7b119d9dedffeadf1164c776f7323d53.jpg"/>