Final answer:
The essential requirement for a stocked handwashing sink is soap and water, as they are critical for removing pathogens and preventing the spread of diseases like COVID-19.
Step-by-step explanation:
The question pertains to one requirement for a stocked handwashing sink. According to CDC handwashing recommendations, the most essential items to have at a handwashing sink are soap and water. This is because they are fundamental to effectively remove and rinse off pathogens from the hands. So, the correct answer to the student's question would be 1) Soap and water. While paper towels and hand sanitizer are useful, soap and water are necessary for the proper handwashing technique that involves lathering and rinsing the hands to prevent the spread of illnesses such as COVID-19. Hand sanitizer is an alternative when soap and water are not available, but it is not the primary requirement for a stocked handwashing sink.