A⁺²is isoelectronic with 'CO₂' & has ( z+2 ) neutrons.

(A) Mass no. of A⁺²is 50

(B) Last electron enters in 's' orbital in element A

(C) No. of Unpaired electron in A is 4

(D) During formation of A⁺², electrons are removed from both s & d subshell.

The total number of electrons in carbon dioxide molecule is 22. As the A2+ ion is isoelectronic with CO₂, therefore the number of electrons (and hence protons) in A are 22 + 2 = 24. The number of neutrons (as given) are z + 2 = 24 + 2 = 26. So the mass number is (24 + 26) = 50. Therefore mass number of A²⁺ ion will be 48. Also, as the atomic number of teh element is 24, therefore the electronic configuration is 4s13d5. Thus the last electron enters the d orbital and number of unpaired electrons in d-orbitals are 5. So the correct answer is (d) -during formation of A⁺², electrons are removed from both s and d subshell.