This is the exact answer:
Bacteria are helpful because they produce oxygen, which our bodies need to breathe, and they help us to digest the food we eat. Bacteria are also helpful because they are used in medicine to help us overcome disease. Bacteria are harmful because they can cause tooth decay and illnesses that can be either common or quite serious.
The answer you chose is right
C. Serving as a Shock absorber and cleaning agent
Because their bodies tell them that they need more oxygen and so breathe faster, and try and get the oxygen their body requires and depends on.
A series of logical steps followed to solve problems.
