An outlier is a data point that lies outside the overall pattern in a distribution.

If an outlier is added to the data set, the data set will either look like this:

{1, 60, 63, 66, 70, 72, 72, 73, 73, 73, 75}

or this:

{60, 63, 66, 70, 72, 72, 73, 73, 73, 75, 1000}

The mean will change since if you add a very big number to the set, the mean will go up. This eliminates choices that have mean, i.e., F, G and H.

The mode which is 73 will not change no matter a very larger number (e.g. 1000) or a very small one (e.g. 10) is added.

The median which is 72 will not change no matter a very larger number (e.g. 1000) or a very small one (e.g. 10) is added.