Teacher: In this task, you're given four sentences of a story written in natural language. The given story is not complete and your job is to complete the story by selecting one of the end sentence choices from (A) and (B), such that the story does not sound complete and coherent, i.e., select an incorrect end sentence.
Teacher: Now, understand the problem? If you are still confused, see the following example:
Sentence1: Rick grew up in a troubled household. Sentence2: He never found good support in family, and turned to gangs. Sentence3: It wasn't long before Rick got shot in a robbery. Sentence4: The incident caused him to turn a new leaf. 
 (A) He is happy now. (B) He joined a gang.
Solution: B
Reason: As mentioned in fourth sentence, the incident turned a new leaf to Rick's life; so, he must be happy now. Also, he was previously in gang, so, this incident cannot make him to join a gang. So, B is incorrect.

Now, solve this instance: Sentence1: Around 11am, the school's fire alarm went off. Sentence2: Rushing towards the door, the students stopped when gunshots rang out. Sentence3: Then the teacher instructed them to hide under their desks. Sentence4: Diving under their desks, the students were petrified. 
 (A) They waited until the incident was over. (B) They then played heads down thumbs up.
Student:
B