The correct answer is option letter C (a problem to resolve). By definition, to have an axe to grind is to have a complaint or dispute that one feels compelled to discuss. For instance, “I think the boss has a bit of an axe to grind with the employees over the way the account was handled”. Here the phrase means that the boss has a problem to work out with the employees. It is difficult to trace the origin of the phrase, but it is commonly attributed to Benjamin Franklin; however, other opinions point to another author who also lived in Pennsylvania, USA.