$$(5\times5\times5\times5\times5\times5)^{4}\times(5\times5)^{6}\div(5)^{2}=(25)^{?}$$

$$(5\times5\times5\times5\times5\times5)^{4}\times(5\times5)^{6}\div(5)^{2}=(25)^{12}\times(25)^6\div25$$

                                                                                                             =$$(25)^{18}\div25$$

                                                                                                             = $$(25)^{17}$$
Hence, the correct value of unknown number is 17.
Therefore, the correct option is B.