Answer:
Internal can be you don't want bad things happening to your body, you don't want drugs affecting your health,etc.External could be you don't want it to affect your family or people around you.For example, like a cigarette if you are smoking in public you can be affecting others passing by or hanging out with you(external)but if it's just you by yourself smoking it is damaging your lungs(internal)
The late stage is where the body and the mind start to fail. It could take weeks or maybe years to get to this stage.
Cross contamination can happen. It is the process in which the microorganisms can be transferred from one substance to another and causing a dangerous effect especially on food thus the answer is Canned goods should be free of dents and any bulging lids to avoid this.
