A rare bacterial culture is being grown in a lab. As time passes, the cells multiply in a specific pattern.
After 1 day, there is only 1 cell.
After 2 days, there are 5 cells.
After 3 days, there are 10 cells.
After 4 days, there are 16 cells.
How many cells will there be after seven days?
A. 40
B. 50
C. 60
D. 70