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I'm currently a junior undergrad in a mathematics program, and emailed a prof at a different school if I would be able to apply as a candidate for a summer project he advertised on the school's website. I'm interested in attending this school for graduate work, and mentioned that to the prof.
In his response, he was very excited about my interest in his project (work in ocean sciences) and in the graduate program, and asked if I could send a transcript. I'm very happy about the response, because the prof was very enthusiastic, but due to (what I now know was and is) depression, my grades took a dip, which can be seen in my transcript. For reference, I've done poorly in a mathematics class and computer science class in my sophomore year (2 Cs, and a D in a genetics course, but that's unrelated to this project). Since then, I've gotten Bs in Calc III and Adv Calc (the only other courses relevant so far).
I know this is not a representation of of my ability, as I've done research projects utilizing the material from classes I've done poorly in, and have done well in the projects. At the same time, I don't want to make excuses for myself, and I don't know if it's fair to disclose that information to the prof to make him choose between a candidate like me, and someone else who is "normal".
How should I respond to this? Should I tell him I can't do his project because my grades aren't up to par, or should I try and explain myself?