16. Look at this series: 80, 10, 70, 15, 60, … What number should come next?

A. 20
B. 25
C. 30
D. 50

17. Look at this series: 2, 6, 18, 54, … What number should come next?

A. 108
B. 148
C. 162
D. 216

18. Look at this series: 5.2, 4.8, 4.4, 4, … What number should come next?

A. 3
B. 3.3
C. 3.5
D. 3.6

19. Look at this series: 8, 6, 9, 23, 87 , … What number should come next?

A. 128
B. 226
C. 324
D. 429