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! :)
Answer:
A. My mother, a doctor, hopes that I follow her career path.
Explanation:
The subject my mother preceding the appositive provides sufficient identification on its own, so you need to use commas around the appositive a doctor.
the letter c is the right answer and thw best