Answer:
a. convince the teacher that the wrong grade was given in hopes of receiving a higher grade.
Step-by-step explanation:
In the letter signed by Gradin Grubber, the student was evidently pained for receiving a low score on a test he put his best into. He explained to the teacher how much effort he invested in the essay and also wrote that the teacher should also have spent as much effort in grading the essay.
While acknowledging that teachers are likely to make mistakes, he explained that important papers like the one he was just graded on should receive more attention. The purpose of this letter is to convince the teacher that the wrong grade was given in hopes of receiving a higher grade.