What is the total number of transition series of $d$-block elements?

Which of the following does not represent the correct order of the property indicated?

$Cr^{2+}$ has a magnetic moment same as that of

Which of the following elements are not regarded as transition elements?

Number of electrons in the penultimate shell of $d-$block elements.

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.