Which of the following statements is true?
A. Isotopes have the same physical properties as the normal atom but different chemical properties.
B. Isotopes have the same chemical properties as the normal atom but different physical properties.
C. Isotopes of the same element have the same number of protons and neutrons. D. If an isotope of one element has the same atomic mass as another element, they will have the same properties.

We know that chemical properties depend on the number of electrons. We know that number of electrons is equal to the atomic number. So the chemical properties of isotopes are same.

Mass number influences the mass of the element. Mass influences the various physical properties.

Thus isotopes having different mass numbers have different physical properties.

So the statement A is false but B is true.

Number of neutrons is equal to the difference between mass number and atomic number.

Since isotopes have different mass numbers, the number of neutrons in different isotopes is different.

So statement C is false.

If an isotope of 1 element has the same atomic mass as another element then they would have same physical properties.

However, their chemical properties would be different.

Since option D does not mention physical or chemical properties, we should assume it means chemical properties. Hence it is false.