df-Block

The lanthanide contraction is responsible for the fact that

  1. Zr and Hf have about the same radius
  2. Zr and Y have about the same radius
  3. Zr and Zn have the same oxidation state
  4. Zr and Nb have similar oxidation state

Answer

In each vertical column of transition elements, the elements of second and third transition series resemble each other more closely than the elements of first and second transition series on account of lanthanide contraction.

The pairs of elements such as Zr-­Hf, Mo-­W, Nb-­Ta, etc possess almost the same properties.

The correct option is A.