

Good luck.I got a letter from my Organic II professor and I got a B. As long as it's someone who knows you well and can speak of you on a personal level, it should be fine.
But to be seriously considered for med school, most of our grades must be As, so does an applicant who requests a LOR from a "B" teacher lack confidence to approach any of the "A" teachers to request a LOR instead of going with the B teacher? (this last point is hypothetical from an admissions committee person)
Random musing:
It's a classic conundrum it seems. True all around. Inevitably, classes seem to fall into one of the two following scenarios.
(1) You do well in the class -- why are you going to spend a lot of time going to office hours? To sound like an annoying know-it-all prick?
(2) You do poorly in the class -- you go to office hours and develop a relationship with the prof. S/he learns more about you, your goals, desires, dreams...and that somehow, you did poorly in his/her class. So you're a hard-worker for whom it didn't pay off.
Sadly, neither situation is incredibly conducive to rec letters.
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OP, I'm sure a B+ is just fine. I'm sure this prof is a good choice if he knows about you. After all, the ADCOMs have your grades already. They know that you could have chosen someone else.
Good luck.
The professors I chose were ones that I talked to about subjects other than class. Even if you're doing well, you can go to office hours to ask about a particularly difficult problem. You can also ask them to look over the mistakes on your test, or something along those lines. Then, if the professor isnt busy, you stay and talk to them a little bit. Do it three or four times, and then you start a relationship with the professor that can result in a good LOR. Also a good idea to make yourself noticed in class, whether by asking questions or participating in discussion or just anything that makes you not just another face in the crowd.Random musing:
It's a classic conundrum it seems. True all around. Inevitably, classes seem to fall into one of the two following scenarios.
(1) You do well in the class -- why are you going to spend a lot of time going to office hours? To sound like an annoying know-it-all prick?
(2) You do poorly in the class -- you go to office hours and develop a relationship with the prof. S/he learns more about you, your goals, desires, dreams...and that somehow, you did poorly in his/her class. So you're a hard-worker for whom it didn't pay off.
Sadly, neither situation is incredibly conducive to rec letters.
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OP, I'm sure a B+ is just fine. I'm sure this prof is a good choice if he knows about you. After all, the ADCOMs have your grades already. They know that you could have chosen someone else.
Good luck.