How many such pairs of letters are there in the word BRIGHTEN each of which has as many letters between them in the word as in the English alphabet ?

Given word: BRIGHTEN
We need to find out the pairs of words which have same number of letters between them as there are in english alphabets.
So we can start with the first letter and check for possible pairs. BR is not a possible pair since B and R have 15 letters between them.
BI is also not possible as there should be 6 letters between them but here, we only have 1. So proceeding in a similar manner we can see that following pairs meet our requirement
IE IN GH
So there are 3 pairs which have same number of letters between them in the given word as there are in English alphabets. So the correct option is D