Which action can best limit the transmission of pathogens by direct contact? a. using mosquito netting b. washing vegetables c. washing hands d. drinking only clean water

I find 
C. Washing hands
the best answer as it is commonsense to wash your hands to help with protecting you, and others from pathogens. It also explains 'Direct Contact' so it must be something to do with 'hands'

Ican only answer your first question, a machine is like a human body because it's a little similar. they both almost work like the same.