The answer is D.
"Keep", "factor", and "calculate" are all verbs in the list of things the new system allows teachers to do. The other sentences are inconsistent with their list of verbs/adjectives/nouns. Thus, option D is the only one that is grammatically correct.
I am not too good at explaining, so let me know if you are still confused.
Hope this helps! :)
I'm not sure if there were specific answer choices but using complex words actually makes your statement rather unclear, especially assuming they are words the average person wouldn't know or understand.
1. House of dusk- dark, whispers in the background
2.dark
