`2m` white counters and `2n` red counters are arranged in a straight line with `(m+n)` counters on each side of central mark. The number of ways of arranging the counters, so that the arrangements are symmetrical with respect to the central mark is `(A)` `.^(m+n)C_m` `(B)` `.^(2m+2n)C_(2m)` `(C)` `1/2 ((m+n)!)/(m! n!)` `(D)` None of these