Which pair of elements from following has halt filled d-orbital in observed electronic configuration?

Calculate the radius of metal atom if it forms bec unit cell having edge length 530 pm.

Calculate the concentration of weak monobasic acid if its degree of dissociation and dissociation constant are $5.0 \times 10^{-4}$ and $5.0 \times 10^{-9}$ respectively.

Which of the following is a secondary allylic alcohol?