Answer the question according to the letter series given below.
$$\text{HDYSMWNBQPOCRTBLZVEGUF}$$

Which two neighbours in the given arrangement are farthest in the alphabetical order?

To find which adjacent pair (neighbours) in the arrangement has the largest absolute distance in standard alphabetical positions ($\text{A}=1,\text{B}=2,\dots ,\text{Z}=26$), let's evaluate the given options step-by-step:
1. Pair B and Q:
* Alphabetical position of $\text{B}=2$
* Alphabetical position of $\text{Q}=17$
* Absolute distance = $|2-17|=15$

2. Pair D and Y:
* Alphabetical position of $\text{D}=4$
* Alphabetical position of $\text{Y}=25$
* Absolute distance = $|4-25|=21$

3. Pair U and F:
* Alphabetical position of $\text{U}=21$
* Alphabetical position of $\text{F}=6$
* Absolute distance = $|21-6|=15$

4. Pair V and E:
* Alphabetical position of $\text{V}=22$
* Alphabetical position of $\text{E}=5$
* Absolute distance = $|22-5|=17$

Comparing the distances: $15,21,15,$ and $17$. The pair with the maximum alphabetical gap is D and Y with a distance of $21$.