Answer: Option D
In this series, every alternate number seems to be increasing by 1 and decreasing by 1.
So, the missing number should be between 14 and 20 and should be 1 less than 20.
Let's find the pattern between the two adjacent numbers:

• 8 - 3 = 5
• 6 + 5 = 11
• 14 - 6 = 8
• ? + 8 = 20

Therefore, the missing number should be 20 - 8 = 12.
Hence, the correct answer is option D) 12.
Key takeaways and formulas:

• In a number series problem, we need to observe the pattern between the given numbers to find the missing number.
• Common patterns include arithmetic and geometric progressions, alternating increases or decreases, squares or cubes of numbers, etc.
• To find the pattern, we can look for the difference between adjacent numbers or the ratio between them.
• Once we find the pattern, we can extend it to the missing number to get the answer.
• It is important to check our answer by verifying it with the given series.

If you think the solution is wrong then please provide your own solution below in the comments section .