题目:设随机变量X的分布律为P{X=k}=λ^k(2-λ),k=0,1,2,其中0<λ<1,则E(X)= _______.A. 0B. (2λ-λ2)/(2-λ)2C. (2λ-λ2)/(2-λ)D. λ/(2-λ)