The maximum number of permutation of 2n letters in which there are only `a's and b's` taken all at a time is given by

Options

A. `""^(2n)C_(n)`
B. `(2)/(1).(6)/(2).(10)/(3)……(4n-6)/(n-1).(4n-2)/(n)`
C. `(n +1)/(1).(n+2)/(2).(n+3)/(3).(n+4)/(4)…..(2n-1)/(n-1).(2n)/(n)`
D. `(2^(n).[1.3.5……..(2n-3)(2n -1)])/(n!)`

Answer

A, B, C, D