The answer is b: hats.
Explanation for each option:
a. Gloves: Wearing gloves while working on rotating equipment can be hazardous because they can get caught in the machinery, leading to potential injury.
b. Hats: Generally, hats do not pose a significant risk when working with rotating equipment, as they are less likely to get caught in the machinery compared to other items like gloves, watches, or rings.
c. Watches: Wearing watches can be dangerous around rotating equipment because they can get caught, leading to injury.
d. Rings: Rings can also pose a risk as they can easily get caught in moving parts, potentially causing injury.
Summary: Among the options provided, hats are the least likely to pose a problem when working on rotating equipment, making them the correct choice for this question.