With reference to Isotopes', which of the following statements is/are correct?1.Atoms with identical atomic numbers but different atomic mass numbers are known as isotopes.2.Protium, Deuterium and Tritium are isotopes of carbon.Select the correct answer from the code given below:

1. A

   Only 2

   Only 2. Protium, deuterium, tritium are hydrogen isotopes, not carbon.

2. B

   Neither 1 nor 2

   Neither. Statement 1 is the definition.

3. C

   Both 1 and 2

   Both. Statement 2 names the wrong element.

4. D

   Only 1

   Only 1. Same Z, different A: isotopes. The three named nuclides are hydrogen.

Summary. Official key is (d) only 1. Isotope definition holds. P, D, T are hydrogen.