If oxygen is not available to a muscle cell, pyruvic acid is changed to and builds up in the muscle cell.

The reduction of pyruvate forms a molecule called LACTATE.  When human muscle cells doesn’t consist enough oxygen to convert organic molecules into ATP through cellular respiration, then it is called LACTIC ACID FERMENTATION. Instead of entering the mitochondria and being converted to acetyl CoA, pyruvate is reduced an electron is given, which is also a product of glycolysis. 

you didn't give any options but heres what i can tell you: an inference is likely to change based on additional observations. the latter is something that you have seen or sensed using your sensory organs while the former is like a conclusion out from what you have observed.