There are 12 classes in one grade, and the students in each class rank from 1 to 50. In order to exchange learning experience, students in each class 14 are required to stay and communicate.

When the total capacity n is large, systematic sampling is adopted. The total population is divided into several parts at equal intervals. At this time, the interval is usually predetermined. In the 1 section, a starting number is determined by simple random sampling. On the basis of this number, an integer multiple of the interval is added as the sampling number.

In this question, the students in each class are arranged from 1 to 50.

Students with class number 14 need to stay and communicate.

The samples thus selected adopt a systematic sampling method,

So choose a.