Answer:
correct
Step-by-step explanation:
"The illustrations will help you to discern the difference between sentences that are carefully constructed and sentences that are thrown together."
The part that's underlined uses parallel structure. Parallel structure is basically showing two things in a sentence using the same word choice to show that they have equal importance. They use "and" to seperate the two parallel parts. Notice "that are" are both used in both parts of the parallel structure so it's correct.
Here's a wrong version of parallel structure:
"sentence that are carefully constructed and sentences that's thrown together."
Hope this helped :)