Answer:
b is the answer ' histology '
It's a type of drug, I'm pretty sure it's related to ecstacy in some way. Please do not do drugs, they're very harmful to not only you and your body but the people surrounding you, stay safe!
In a study, the independent variable is the thing that you change to see how the change produces different results. In this study, the independent variable would be the use of nicotine.
If there are no multiple choices then i just thonk he should quit
Watery, runny eyes
Runny nose
Sneezing
Nasal congestion
Itchy rashes or hives.
Hope this helps, and Brainliest is really appreciated