Answer:
a. exposition
The exposition in the story occurs when zombies began to appear in different South Korean cities, and specifically, in the train where the main characters are located.
b. conflict
The conflict is represented by the literal fight between the passengers of the train, including the main characters, and the zombies, as they try to trap the zombies inside a few wagons of the trian, being unsuccesful in doing so.
c. climax
The climax arguably occurs when the passengers try to change the train they are boarding, and have to cross a whole train station. Zombies follow soon, and kill many passengers, including a few of the main characters.
d. resolution?
The conflict ends when the two main characters (Father and daughter) manage to escape from the zombie horde.