Answer:
The sentence which possesses a tone that would be most appealing to a professor is:
d. Please allow me the opportunity to argue for a better grade.
Step-by-step explanation:
A situation such as this, in which you need to address someone who is hierarchically superior to you and who has the power to change something that affects you, demands a certain type of tone and style. Since this refers to you addressing a professor, we can assume the use of formal language will be seen in more of a positive light. But that is not all. Politeness and diplomacy are also crucial. Take a look at option B, for instance. Even though the language is fine, it lacks diplomacy. It accuses the professor of having been sloppy, which will most likely offend him.
The best option is letter D. It uses formal language, and the sentence itself is polite, without any unnecessary assumptions or accusations.