Which of the following data sets or plots could have a regression line with a negative y-intercept?

Select the correct answer below:

The difference in height between two twins (shorter twin - taller twin), plotted as a function of age.

The number of people saved from a well, as a function of the number of years since the town was founded.

The height of the taller of two twins, as a function of age.

The number of people who have fallen into a well, plotted as a function of the number of years since the town was founded.