Correct Answer: 33
Explanation:
The given series follows a pattern that,
+4, +6, +8, +10, +12...
5
5 + 4 = 9
9 + 6 = 15
15 + 8 = 23
23 + 10 = 33
33 + 12 = 45
Hence, the missing number in the series is 33.