The rules of logs apply.
.. a*log(b) = log(b^a)
.. log(a) +log(b) = log(ab)
The 2nd selection would be correct if it had parentheses around the argument of the log function. It is the best choice of those offered.
[tex] log_{5}((25 x^{6}) \sqrt[3]{ x^{2} +6}) [/tex]