In ground state of Cr24, number of orbitals with paired and unpaired electron:-

a]10 b]15 c]18

Hiii Tanusri

 Atomic number of cr is 24 

So, Electronic configueration of chromium is Ar 18 3d^5 4s^1

So, the number of unpaired electron left in the ground state of chromium is 6.

The electronic configuration of Cr: 1s2 2s2 2p6 3s2 3p6 4s1 4d5.

So in s subshell contain 1 orbital, p subshell contain 3 orbitals whereas d orbital contains 5 orbitals  each.considering paired electrons there are 9 orbitals which are filled upto 3p6 and the rest are unpaired electrons which occupy 6 orbitals (one in 4s1 and 5 in 4d5).

So the answer is (b)