PhD selection discrepancy I've got 2 interview offers for a PhD application from 2 different professors (say A and B). Prof.A contacted me regarding the application in mid Sept. and informed me that he'd conduct an interview in mid. Oct while Prof. B contacted me a few days ago and informed that he'd conduct an interview next week.

While talking with Prof. B (via Email) today, I somehow happened to mention about Prof. A and an interview offer from him. So, Prof. B stated that he'd not be able to conduct an interview with me and informed me that I would have to go with either of the professors for an interview.

I don't want to blow my chance for an interview with Prof. B since it'd be extremely risky to just wait for an interview with Prof. A, as the result of an interview with Prof. A is not assured.

I may be chasing two hares at a time here, but I don't want to take any risks here unless they are unavoidable. So, what am I to do now?

P.S.: I've not yet contacted Prof. A regarding my situation yet.
Unless Prof B has made you a firm offer in writing, for a PhD, then he is being unreasonable. This is a terrible situation to put you in: he wants you to commit to him, withdraw all your other applications, whereas he has obviously not decided yet that he is going to take you as a student. If he takes you, then no harm done; but if he takes someone else, you're screwed. Nobody should apply to just one job... or even just two! The risk is too great. Everybody should understand this, and someone who doesn't understand isn't somebody you want to work with.

However as Dawn says in the comments, you should try to clarify the situation. Explain to Prof B that the interview with Prof A is just an interview, not a firm offer; exactly like the one with him. If he still insists that you only go to one interview... I would think very hard about continuing with him.