Final answer:
OSHA requires that portable ladder rungs be smooth and round to decrease falls by providing a stable foothold.
Step-by-step explanation:
In order to decrease falls when using portable ladders, OSHA (Occupational Safety and Health Administration) has specific requirements for ladder construction to ensure safety. According to these regulations, ladder rungs must not be slippery; they need to be designed to minimize slip hazards. Therefore, the correct answer is that ladder rungs should be C) Smooth and round, which helps prevent accidents and falls by providing a stable foothold for the user.