答案:B解析:因为$X$服从参数为$\lambda$的泊松分布,所以$P(X = k) = \frac{\lambda^k e^{\lambda}}{k!}$。由$P(X = 1) = P(X = 2)$,可得$\lambda e^{\lambda} = \frac{\lambda^2 e^{\lambda}}{2}$,解得$\lambda = 2$。 本题来源 题目:设随机变量$X$服从参数为$\lambda...