What is the difference between disease causing bacteria and viruses?

a
Viruses can live outside the human body and bacteria cannot.
b
Disease-causing bacteria trigger illnesses, by living inside the body and on the surface of the body. A virus cannot survive outside the body's cells. It causes illnesses by invading healthy cells and reproducing.
c
Bacteria are multi-celled organisms and viruses are single-celled organisms.
d
none of these are correct