I'm in grade 11 and ever since I chose subjects, my family always told me that taking physics "opens doors" to every other career in life. The thing is, I've been hating it ever since I chose it. I only get C's and I don't think that's good at all. Do you think I should drop it? Considering that for what I want to do in life, I really only need biology- which I'm already taking.

A biologist DOES need a solid background in all the sciences, as well as math.

What if you want to become an expert in something like the physical motion of very fast animals (just one of thousands of specialties)? You do need physics.
Saying 'Considering that for what I want to do in life, I really only need biology' is very, very naive.
Taking groups of subjects is called 'transfer of knowledge.'
These days, any advanced career also requires lots of math, statistics, and computer skills.

Why are you asking this in June? Do you live somewhere that has school beginning now?
What is it that you want to do in biology?

I never took physics and have multiple degrees. It all depends on what the prerequisites are for your university.

It really depends on what you want to do and what the University you decide to go to, demands. If they require Physics for you to get into the program you want and the career you want, then you need to take it. If they don't require physics, then drop it.

First how far along are you, high school should be getting over, in most areas??

And a C is not bad, nothing wrong about passing the class with C score.

It is required for some universities in some majors.