This is a case (just one of many) where the examiners have made some simplfiying assumptons, but have not stated what these assumptions were.
All they really want you to do is to note that reducing frequency reduces inductive reactance so for a given applied voltage the current through inductors will increase.
As you have said the situation is much more complicated in real circuits where different types of component are connected in various ways.
But if you look at the other options, the voltage regulator should prevent these effects unless the RPM is very much lower than standard.