D. Trachea, is the answer.
To use the restroom. If we don’t do our business our bladder would literally explode. We also need to go to shower/bathe to have good hygiene. Also to change tampons/pads (for females)
Individual Health is focused on one patient, public health is focused on health of populations
It's a fun, and interesting thing to do. It's a great help towards your community and you benefit in the end with people and working skills. It's also great if you need some extra curriculars for your college applications.