How many protons are present in an atom which has an atomic number of 35?

The atomic number Z of an element can be defined as the number of protons  present in the nucleus of each atom of that element. Also known as the number of protons. 
Each element has a unique atomic number because each element has a unique and different number of protons. 
Now we know that the atom with atomic number  35 is bromine (Br). 
Since the number of protons present in an atom is equal to the atomic number, there are 35 protons  in a bromine atom.

Hence, option A is correct.