Choose the odd one out.

The odd one out is C. RWB. The other options are all three-letter acronyms that are commonly used in the English language. CHM stands for chemistry, HMR stands for human resources, DIN stands for Deutsches Institut für Normung (German Institute for Standardization), and LPU stands for linear predictive coding. RWB, on the other hand, is not a commonly used three-letter acronym. It could stand for “red, white, and blue,” but this is not a common usage.