I don’t know if this is the answer but I would say “to help teachers make sure students don’t plagiarize”
Answer: A
Explanation: A hoax is something that’s untrue, it’s deceits people purposefully so they can sometimes follow a certain path or reasoning.
B. A possessive noun should have its instead of it's (which is a contraction for it is).
For A. Diana is a singular noun and the apostrophe should come after the r instead of after the s.
For C. The duck would've dunked ITS instead of IT'S beak since it is possessive.
For D. You do not need to put an apostrophe since theirs is already a possessive noun.