Which one of the following options is correct for the given data in the table?

The manager asked the team to complete the project _______ the end of the week.
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?
\(2, 6, 12, 20, 30, \ ?\)