A force is a push or pull to an object
Decay of Schizomycetes waste present in waste water leads to unpleasant smell.
These microorganisms, known as iron and sulfur bacteria, cause hydrogen sulfide to be found in water supplies. They include crenothrix and beggiatoa. Most often found in groundwater supplies, they produce an offensive odor of decaying matter. (I'm not sure)
Should be an air tight seal
knowledge of first aid ... eg St John Ambulance, Red Cross etc. I think that everyone in a school should be taught First Aid.