A professor at the university has taken a sabbatical to ...

[YanZ857]

A professor at the university has taken a sabbatical to research [question text deleted]

Dear instructors

I pick "D" but the OA is "E".
Are there any differences between "research" and "research on"?
And can ", written while he lived in France" modify "the books of James Baldwin"?

thank you so much

[Sage Pearce-Higgins]

This looks like SC 698 from OG2019. Unfortunately we can't post this copyright material on the forum (please read the guidelines before posting); however, there's a great explanation on the Navigator app: https://www.manhattanprep.com/atlas/resource/58

There is, indeed, a difference between 'research X' and 'research on X'. Look at these (correct) examples:
1. Yan is a scientist and researches genetic diseases.
2. Yan is a scientist and conducts research on people with genetic diseases.
3. Yan spends all his time researching genetic diseases; he even researches on the train.

Perhaps the important idioms here are 'to research X' and 'to conduct research on X'.