Which statements about the isotopes of chlorine, $_{{\text{17}}}^{{\text{35}}}{\text{Cl}}$ and $_{{\text{17}}}^{{\text{37}}}{\text{Cl}}$, are correct?

I.     They have the same chemical properties.

II.     They have the same atomic number.

III.     They have the same physical properties.

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

A