Question

how often should people wash their hands to maintain good personal hygiene?
once per day
at least twice per week
whenever their hands are visibly dirty
whenever they touch unclean surfaces

Explanation:

Good personal - hygiene hand - washing includes washing hands whenever they are visibly dirty and whenever unclean surfaces are touched. Washing hands only once a day or at least twice a week is not sufficient for maintaining good hygiene.

Answer:

C. whenever their hands are visibly dirty
D. whenever they touch unclean surfaces