Before answering to the question, let us analyze a little bit the meaning of both concepts:
Inferencing is the inner mental ability of reasoning to analyze different situations or problems and to produce a general idea or rule about such situation or problems. This is could be better understood with a little analysis of the Inductive reasoning, but I think it is pretty clear so far.
Inflection refers to the ability of the vocal spectrum to change the tone of words to convey different meaning or purposes.
So, having mentioned the former, the statement that contrast inferencing and inflection is:
Inferencing occurs in the mind and inflection occurs with the voice.
