According to the formula,

The average of 'n' multiples of a number =$\frac{\mathrm{Number}\times \left(\mathrm{n}+1\right)}{2}$

∴ n=9, number=5

∴ Required average =$\frac{5\times \left(9+1\right)}{2}=\frac{50}{2}=25$

Hence, Option B is correct.