The dot plots represent the distributions of values in Data Set A and Data Set B.
Data Set A is as shown in the left plot.
Data Set B is similar to the right plot, but one of the values of 16 is replaced with a value of 20.

Which of the following statements must be true?
I. The median of data set A is equal to the median of data set B.
II. The standard deviation of data set A is greater than the standard deviation of data set B.