Which of the Following Statistics Is a Ratio

Which of the following statistics is a ratio?

A) The firefighters saved 23 people from the apartment fire.
B) Seventy-five percent of my class is Christian, 5% Jewish, and 20% prefer not to answer.
C) The most common score on the test was a 92%.
D) Half of the plumbers in our city earn more than $52,000 per year, while the other half earn less.
E) For every three weeks that I work, I earn one day of paid vacation.