Which of the Following Studies Is an Example of a Longitudinal

Which of the following studies is an example of a longitudinal design?

A) Dr. Finn's study in which he measured job commitment in a group of Japanese factory workers and in a group of Mexican factory workers
B) Dr. Stabler's study in which he measured people's frequency of playing video games in ninth grade and their aggressive behaviors in 12th grade
C) Dr. Benson's study in which she measured people's spatial manipulation ability in August and measured their ability again in May after they had taken two semesters of art classes
D) Dr. Tutola's study in which he measured the daily stress of a group of married men and the daily happiness of their spouses