单选题

服从均值为10的正态分布，已知P(X<=30)=0.7，求P(X&l...

Question

服从均值为10的正态分布，已知P(X<=30)=0.7，求P(X<=-10)

A. 3/10

B. 2/10

C. 1/2

D. 2/5