Answer:
The correct answer is <u>conducting a controlled experiment.</u>
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)
You may miss the symptoms but there are symptoms and they can be detected and life threatening. Especially if we consider AIDS as an STD.
I believe the answer to be B. False
