16. 

2, 5, 9, ?, 20, 27

A. 14
B. 16
C. 18
D. 24

17. 

2, 3, 3, 5, 10, 13, ?, 43, 172, 177

A. 23
B. 38
C. 39
D. 40

18. 

9, 27, 31, 155, 161, 1127, ?

A. 316
B. 1135
C. 1288
D. 2254

19. 

2, 1, 2, 4, 4, 5, 6, 7, 8, 8, 10, 11, ?

A. 9
B. 10
C. 11
D. 12

20. 

Which of the following will not be a number of the series 1, 8, 27, 64, 125,.....?

A. 256
B. 512
C. 729
D. 1000