Front

scent

Back

smell

Front

immune system

Back

cells and tissues that recognize and attack foreign substances in the body

Front

respiratory illness

Back

infection, disease, inflammation of the airways

Front

leftovers

Back

food remaining from a meal

Front

biodegradable

Back

Able to be broken down naturally

Front

go off

Back

go bad (food/drink)

Front

sewage

Back

The water and human wastes that are washed down sinks, toilets, and showers

Front

stench

Back

a strong and very unpleasant smell.