We want to find rigid motions to get from NAV to BCY.
The question already shows an intermediate N'A'V' to help.
We can see that the distances from the vertexes of NAV to the x-axis are equal to the distances from the vertexes of N'A'V' to the y-axis.
Thus, we can get from NAV to N'A'V' by doiong a reflection over the x-axis.
Now, N'A'V' are turned in the same way, so we just need to translate it. The y values of the vertexes of N'A'V' and BCY are the same and all the BCY vertexes are at exactly 5 units from the corresponding N'A'V' vertexes, which means we need a Translation only in the x values by -5 units (it is negative because it is to the left).
So, the sequence of rigid motions is a Reflection over the x-axis abd then a tranlation by (x-5,y+0), which corresponds to the third alternative.