Which element would not have similar properties with calcium?
  a
k, potassium
  b
sr, strontium
  c
mg, magnesium
  d
be, beryllium

Potassium would not have similar properties because it is the alkali metals, not alkali earth metals

Most smaller stars don't have a radiative zone.

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.