Please answer the following question: Extract the answer to the question from the following context. Question: How does the sun come into contact with bottles when using SODIS? Context: Solar water disinfection (SODIS) involves exposing water-filled plastic polyethylene terephthalate (PET) bottles to sunlight for several hours. Exposure times vary depending on weather and climate from a minimum of six hours to two days during fully overcast conditions. It is recommended by the World Health Organization as a viable method for household water treatment and safe storage. Over two million people in developing countries use this method for their daily drinking water.
Answer:
exposing water-filled plastic polyethylene terephthalate (PET) bottles to sunlight