Refer to the Following Paragraph to Answer the Questions Below

Multiple Choice

Refer to the following paragraph to answer the questions below.
Professor Alco Drunkman studied class level and drinking behavior at Wild State University in Boozville, Texas. Every student is required to live in one of six twenty-story-tall dormitories, and has a single room. All dormitory room phone numbers began with the prefix 747 or 757 (e.g., phone numbers are 747-0001 to 757-9999) . He used the student telephone directory, and after a random start selected every 15th student. He then mailed a questionnaire to the 1,000 students selected and had two follow-up postcard reminders. A total of 900 students returned questionnaires. Later, he asked the university registrar whether any students were omitted from the directory.
-The registrar's office stated that 3,000 currently-enrolled student names were omitted from the directory, but everyone in the directory was still enrolled. With this revised estimate of the population and final number of students on which he has data, what is Drunkman's actual sampling ratio?

A) 1 percent
B) 5 percent
C) 8 percent
D) 10 percent
E) 15 percent