A variable takes the values of `0`,`1`,`2`,.....,`n` with frequencies proportional to the binomial coefficients `C_0`,`C_1`,`C_2`,......,`C_n`, then mean of the distribution is
(1)  `(n(n+1))/4`      (2)  `n/2`      (3)  `(n(n-1))/2`      (4)  `(n(n+1))/2`