Hello there!
Negative peer pressure is when you are being pressured to do something bad. An example would be someone telling you that you have to do drugs with them or else they will spread a rumor about you.
a.inviting you to go out with a group of friends - This is incorrect. Not only is this not forcing you to do something, but this is a positive thing.
b.exercising with you - This is incorrect. Not only is this not forcing you to do something, this is a positive thing that will benefit your health.
c.bullying you into doing something- This is correct. They are attempting to force you into doing something that you most likely don't want to do.
d.studying for tests together- This is incorrect Not only is this not forcing you to do something, this is a positive thing that will most likely help you in school.
The answer is C.
I hope I helped!
Let me know if you need anything else!
~ Zoe