The correct option is B AND C.
An isotope is defined as two or more forms of the same element which contain equal number of protons but different number of neutrons in their nuclei, hence they differ in relative atomic mass but not in chemical properties.
Thus, isotopes has the same number of protons but differ in number of neutrons. Due to this fact, isotopes always have the same atomic number but different mass number. You will notice that the atomic number given for elements B and C are the same [101].
