Which of the following yields a simple random sample?

A、All students in a class are divided into groups of 15. One student is randomly chosen from the first group, the remaining observations are every 15th student thereafter.;
B、The best 15 students, according to the opinion of the instructor, in a class are selected.;
C、The names of 50 students in a class are written on 50 different pieces of paper and put in a hat. The first 15 pieces of paper are selected blindly one at a time without replacing them back in the hat after shuffling the papers thoroughly.;
D、 All students in a class are divided into groups according to the rows in which they are seated. One of the groups is randomly selected.