1/7 as presented, or 1/8 if the word "students" were properly spelled.
If you are looking for a word that contains all five letters, it is "onion."
Darshan and duramen are the seven letters word that start with D and end with N.
The word "zone" contains both letters.
There are 3 letters: B, A, and N. The A is repeated twice more and the N once more.
run
The word inkiest can be made with those letters.
Se~nora
neutral
arson
The longest word is 6 letters: nocent
enchanted
The letters N g e a b can be unscrambled into the word "began."