**Answer:**

Option C

**Explanation:**

Let us divide the letters of the given word into pairs and label these pairs from 1 to 6.

$\frac{BR}{ 1}, \frac{EA}{2}, \frac{KT}{3}, \frac{HR}{4}, \frac{OU}{5}, \frac{GH}{6}$

Clearly, the code contains these pairs arranged in order 2,5,4, 1, 6, 3.

Dividing the letters of the word DISTRIBUTION in pairs, we have :

$\frac{DI}{ 1}, \frac{ST}{2}, \frac{RI}{3}, \frac{BU}{4}, \frac{TI}{5}, \frac{ON}{6}$

Arranging these in the order 2, 5, 4,1,6, 3, we get the required code i.e. STTIBUDIONRI. Hence, the answer is (c).