Final answer:
The correct answer is 1) Well. According to Leviticus 11:36, a well is regarded as clean even if something unclean falls into it, highlighting beliefs about the natural purity of underground water sources.
Step-by-step explanation:
If something unclean fell into a cistern that collected water or a well, it was still considered clean (Lev. 11:36). The answer to the student's question is 1) Well. The Bible passage infers that sources of spring water, such as wells, have a self-purifying quality, an idea that echoes some ancient and even some modern views on the natural cleanliness of flowing underground sources. However, it is crucial to remember that in contemporary times, monitoring water quality to prevent contamination from nearby sources, such as cesspits, is important for health and safety.