The second and third rows of transition elements resemble each other much more than they resemble the first row. Explain why?

(N/A) The properties of elements of the second and third transition series are similar due to the lanthanoid contraction.
As a result of the lanthanoid contraction,the elements of the third transition series have atomic radii that are almost identical to those of the corresponding elements in the second transition series.
This similarity in atomic radii leads to a significant similarity in their chemical and physical properties.