There are 5 vowels in the given word which are 4E's&1I.
Since they have to always occur together we take them as a single object EEEEI for the time being.
This single object together with 7 remaining object will account for 8 objects.
There 8 objects in which there are 3N's&2D's can be arrangement in 3!2!8! ways.
Corresponding to each of their arrangements the 5 vowels E,E,E,E&I which can be arranged in 4!5!
Hence, required number of arrangements.
=3!2!8!×4!5!=16800
Hence this is the correct option.