A rectangular board of 8 columns has squares numbered beginning in the upper left corner and moving left to right so row one is numbered 1 through 8 , row two is 9 through 16 , and so on. A student shades square 1, then skips one square and shades square 3 , skip two squares and shades square 6 , ships 3 squares and shades square 10, and continues in this way until there is at least one shaded square in each column. What is the number of the shaded square that first achieves this result?
Answer Choices
A. 36
B. 64
C. 78
D. 91
E. 120