Im not 100% but i think the answer is d. :}
I think a biographical dictionary.
That sentence is an example of parallel structure.
When there is repetition of a specific grammatical form in a sentence, parallelism or a parallel structure is produced. This occurs when you mantain the same pattern for every compared word or idea in your construction. This makes the idea easier to follow by the reader.
Answer:
Music. Find lofi or instrumentals or beats of your favorite songs. Some say music makes your focus bad, but it provides an incentive and helps me slip into the zone. As long as it isn't heavy rock or energetic pop, just some calming music without lyrics, it helps you relax and focus.
If you could give me your insta I might be able to help more by basing it off your interests. Feel free not to though.