Which answer choice best describes the connotation of the word contaminated, and why it is connotated this way?

It contains a positive connotation because when something is contaminated, it contains a harmless substance.
It contains a positive connotation because when something is contaminated, it contains a beneficial substance.
It contains a negative connotation because when something is contaminated, it contains a harmful substance.
It contains a negative connotation because when something is contaminated, it contains an unknown substance.