If the probability function of a random variable $\mathrm{X}$ is given by $P(X=j)=\frac{1}{2^j} ; j=1,2,3, \ldots, \infty$ then the variance of

• Correct answer
  A

  2
• B

  3
• C

  4
• D

  5

Hence, the correct answer is option: 'A'.