Which of the following statements regarding sorting the 'x' column by 'y' is true?
a) Sorting by 'y' is possible even with multiple values in 'y' for the same value in 'x'.
b) Sorting by 'y' is not possible if there are multiple values in 'y' for the same value in 'x'.
c) Sorting by 'y' is always possible regardless of the data in 'y'.
d) Sorting by 'x' is not affected by the values in 'y'.
