I first consider D as the most obvious of parallel construction. I’ll stay with that consideration too, because I think that’s what your teacher would do.

Good luck.

RE:
parallel construction means that you?
A. repeat the forst paragraph of your essay as the last paragraph

B. use the same grammatical construction in all similar headings throughout an outline

C. begin each paragraph of your essay in the same way

D. give both sides of the argument in your essay

C. Use the same grammatical construction in all similar headings throughout an outline.

a would be redundancy; c would be silly; d is just balanced perspective