The professor found himself constantly ________the question: “How could anyone do these things?”
句意：教授发现自己一直在思考一个问题：“怎么可能有人能做这些事？”ponder沉思，考虑。preside主持；负责。pore over审视，审阅。presume推测，假定。因此，本题的正确答案为C。