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.
The answer is D “Plaque can build up and prevent oxygen from reaching the brain”.
A lot of caffeine if you don't wanna ruin your lungs, vaping and smoking are stress relievers and I heard that it helps with homework but since I'm a xc runner that wouldn't be very good on my lungs and I don't recommend it.
D heavy drinking during a pregnancy
