Consider the following:
1. Atomic number
2. Atomic mass
3. Number of protons
4. Number of neutrons
Which among the above is / are same for each of C-12, C-13 and C-14?

Answer: [A] 1 & 3

Isotopes contain equal numbers of protons but different numbers of neutrons. 

This question is a part of GKToday's Integrated IAS General Studies Module