Abromine atom in an excited state could have an electron configuration of(1)2-8-18-6 (2) 2-8-18-7 (3) 2-8-17-7 (4) 2-8-17-8

The answer is (4) 2-8-17-8. The bromine atom at ground state has an electron configuration of 2-8-18-7. When excited, the electron will gain energy and goes from lower layer to upper layer.

It changes food into energy that the organism can use.