Answer: C
For over 20 years, most of the world's computers have used a 32-bit word, particularly in the Intel IA-32 architecture.
The word size is important, because it is:
The Intel Core i5 and similar processors have a 64-bit word, but also have a 32-bit compatibility mode; even if you have one of these more modern processors, it is likely that much of what you do is running in 32-bit mode.