Which of the following pairs has the same size?

$\text{Zr}$ (Zirconium, 4d series) and $\text{Hf}$ (Hafnium, 5d series) belong to the same group. Normally, size increases down a group, but due to Lanthanide Contraction (poor shielding by 4f electrons), the increase in size from $4d$ to $5d$ is offset. Consequently, ${\text{Zr}}^{4+}$ and ${\text{Hf}}^{4+}$ have almost identical ionic radii.