One term in the number series is wrong. Find out the wrong term. 1236, 2346, 3456, 4566, 5686

The answer is $\boxed{\text{B}}$.

In this number series, each number is formed by adding the previous two numbers. For example, $3456$ is formed by adding $2346$ and $1236$.

The only number that does not follow this pattern is $3456$. It should be $3454$, which is formed by adding $2342$ and $1232$.

Here is a table showing the numbers in the series:

Number | Explanation
——- | ——–
1236 | Start of the series
2346 | $1236 + 1210 = 2346$
3454 | $2346 + 1212 = 3454$
4566 | $3454 + 1214 = 4566$
5686 | $4566 + 1216 = 5782$

As you can see, the only number that does not follow the pattern is $3456$. It should be $3454$.