Match List-I with List-II: 
Choose the correct answer from the options given below:
Match List-I with List-II: 
Fill in the blank with the correct option.
The teacher believed that the student’s sudden lack of interest in class was an ..........., as he had always been enthusiastic and attentive.
What comes next in the series?
\(2, 6, 12, 20, 30, \ ?\)