Which of the following numbers will replace the question mark (?) in the given series?
$$5,8,13,?,29,40$$

Let's find the difference between consecutive terms in the given series:
* $8-5=3$
* $13-8=5$

The differences are consecutive odd numbers: $+3,+5,\dots$
Following this pattern, the next differences should be $+7,+9,$ and $+11$.

Let's test this logic:

* Next term $=13+7=20$
* Next term after that $=20+9=29$ (Matches the given series)
* Next term after that $=29+11=40$ (Matches the given series)

Thus, the missing number that replaces the question mark is $20$.