Which of the following forms a colourless solution in aqueous medium?

Which of the following statements is correct?

Which of the following magnetic moment values corresponds to the highest ionization energy for $Mn$?

The metal having the highest melting point is

Determine whether the following statements are True $(T)$ or False $(F)$:
$(a)$ An element or its ion that does not have a completely filled $d$-orbital is considered a transition element.
$(b)$ $Sc$ is a transition element.
$(c)$ $Zn$ is a transition element.
$(d)$ The energy difference between $(n-1)d$ and $ns$ orbitals is high.

Which of the following types of metals make the most efficient catalysts?