Missing Number

1. What is the missing number?

14
4 7 4
5 1 4 1 5
1 2 3 5 3 2 1
1 1 1 1 ? 1 1 1 1

a. 1
b. 2
c. 6
d. 10

Answer:

d

14 = 14
4 + 7 + 4 = 15
5 + 1 + 4 + 1 + 5 = 16
1 + 2 + 3 + 5 + 3 + 2 + 1 = 17
1 + 1 + 1 + 1 + 10 + 1 + 1 + 1 + 1 = 18