Refer to the Following Paragraph to Answer the Questions Below

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.
-Drunkman decided to conduct his study using a telephone interview instead using a mailed questionnaire. Which is the most accurate way to sample?

A) a simple random sample from the directory of the town
B) a systematic sample of the student telephone directory
C) random-digit dialing using the 747 or 757 prefix
D) a quota sample with an equal number of students from each dormitory
E) a stratified sample from 100-, 200-, 300-, and 400-numbered courses