Naturally you have to be careful that you are talking about a reputable school (as opposed to a diploma mill). That being said, most regular universities offer courses online. I took physiology that way. I can't say I'd recommend it for classes with subject matter you find difficult to grasp, though. The biggest issue for me is was that without lecture, I had a hard time narrowing down what was actually crucial to know. Every single concept in the book was equally important to understand. For this reason, I thought it was more difficult than a regular class.

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