It is necessary to note that only a metal that is above another metal in the activity series can displace it from its compound.
The first statement said that titanium reacts with magnesium oxide. The implication of this is that titanium can displace magnesium from its oxide. This is only possible if titanium is above magnesium in the activity series.
The second statement says that sodium reacts with titanium oxide. This implies that sodium metal can displace titanium from its oxide. For this to occur, then sodium must be above titanium in the activity series of metals. Hence the answer above.
