Final answer:
The student's task involves submerging iron nails in various types of water to observe corrosion, which illustrates the chemical process of rust formation that requires both oxygen and water. The experiment also relates to environmental studies, emphasizing the importance of conserving water through methods such as using gray water and collecting rainwater.
Step-by-step explanation:
The question "Gather rainwater, sea water and tap water and________ iron nails" appears to be part of a Chemistry experiment related to the corrosion or oxidation process of iron. When iron nails are submerged in different types of water, they may corrode at different rates. This is because rust formation requires both oxygen and water. According to provided information, an iron nail immersed in deoxygenated water will not rust, as both oxygen and water are needed for rust to develop.
On the other hand, rainwater and oxygen-rich environments will facilitate rust formation. From an environmental perspective, reusing water, like using gray water for irrigation and collecting rainwater in rain barrels for garden use, are effective methods for conserving water resources.