Which stem of equation should omar use?

According to the logarithmic property of the base change, the corrected answer is option four or the last.
 The logarithmic property of base change given that
 loga (b) = logc (b) / logc (a)
 Therefore, the same property applies to this problem and the correct expression for this question is:
 y1 = log (x) / log (6)
 y2 = log (x + 4) / log2