The answer is the first data set because remember, an outlier is a number in a data set that is extremely far away from all of the other numbers.
You can easily tell which one is the outlier, the first data set's outlier is 13, because it is was placed so far away from the other data points.
We know that the first data set is correct because all of the other data sets have numbers that are clustered together.
~Hope I helped!~