Kendy,
While it is easy to claim that the plagues of Egypt could be explained by natural phenomena, it is a much more difficult thing to demonstrate that they were. Depending on how important the subject is to you, you might want to ask the professor for the details of exactly how each plague–as described in Exodus, without changing the text–would have resulted from natural causes.
A professor in Israel a year or two ago explained how Jesus’ walking on water could have a natural explanation. Apparently there is a phenomenon that happens a few times per century in which the water in the Sea of Galilee gets just cold enough that the fresher water (from inflowing streams) freezes while the saltier water (from other streams and in the sea itself) remains liquid. (The Sea of Galilee does not usually freeze at all.) Thus Jesus would have been walking on the ice while the disciples’ boat was in the liquid section. Of course, this explanation neglected the facts that the “ice” was strong enough to support a man, that Peter got out of the boat and walked towards Jesus, and that this happened in the springtime rather than in the dead of winter.
I find that many “natural” explanations leave out important facts like this.