Isotopes of an element have select one: a. the same atomic number and same atomic weight. b. the same atomic number but different atomic weights. c. different atomic numbers but the same atomic weight. d. different atomic numbers and different atomic weights.

Option B same Atomic number and Different Atomic weight

Explanation:

Isotope are those inwhich no of protons (Atomic number) is same and mass number (A=n+Z) is different

Examples: Cl-35& Cl-37

And O-16& O-18

And option C corresponds to Isobars with same mass number and different atomic number.

the dissolution of polymer can be thermodynamically described in 2 steps.