Given the task definition, example input & output, solve the new input case.
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.
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.
Output: B
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.

New input case for you: Sentence1: Bob got a rubix cube for Christmas. Sentence2: He struggled to solve the puzzle. Sentence3: Eventually, he was able to solve half of it. Sentence4: But, the full solution remained elusive. 
 (A) Bob worked hard and then finally solved the puzzle. (B) Bob then gave up on the video game.
Output:
B