Anitha argued that the 3d orbital is filled first, but not 4s orbital, with electrons.
By asking some questions Saritha corrected Anitha's argument.
What would be those questions ?

Explanation

1) How do you calculate the value of the energy of an orbital ?
2) What is the use of (n + l) value ?
3) What is the n + l value of 3s orbital ?
4) What is the n + l value of 3d orbital ? 5) Which orbital, between 3s and 3d has higher n + l value ? 6) Which orbital has higher energy ?
7) According to Aufbau, which one should be filled first with electron ?
8) How do you change your argument ?