It has been given that the point (3,1) is on the graph. For the point (3,1) to be on the graph, the following must hold true:
![1=log_{10}(ax)](https://tex.z-dn.net/?f=%201%3Dlog_%7B10%7D%28ax%29%20)
or ![ax=10^1=10](https://tex.z-dn.net/?f=%20ax%3D10%5E1%3D10%20%20)
Thus, ![x=\frac{10}{a}](https://tex.z-dn.net/?f=%20x%3D%5Cfrac%7B10%7D%7Ba%7D%20%20)
Thus, in order for the point (3,1) to lie on the graph, of all the given options the closest we can get is when we have Option C, that is, when a=3. That will make x=3.33 and thus,
.
Thus, out of the given options only Option C seems to be the most probable answer.