Answer: Option B
Product of all odd natural numbers less than 5000
$$\eqalign{
& = 1 \times 3 \times 5 \times 7 \times ..... \times 4999 \cr
& = \frac{{1 \times 2 \times 3 \times 4 \times 5 \times 6 \times ... \times 5000}}{{2 \times 4 \times 6 \times 8 \times ... \times 5000}} \cr
& = \frac{{5000!}}{{{2^{2500}}\left( {1 \times 2 \times 3 \times 4 \times ... \times 2500} \right)}} \cr
& = \frac{{5000!}}{{{2^{2500}} \times 2500!}} \cr} $$