Which is the best option?

You only have one good option as far as I'm concerned. That's A. Maybe you'll make a new friend, maybe they'll be smart, maybe you'll work great together...think positive and take a chance! If you pick B you'll be stuck doing all the work, and nothing is more frustrating than working with someone who is not smart and is very immature. C brings too much drama, you admitted to not liking the girlfriend, who needs to work with someone you don't really like, not to mention do you really think she'll want to see you and her boyfriend be friendly. I don't think so.... Deffinately pick A! Good luck, it can't be any worse than the other two.