# The electrons,identified by quantum number n and l,(i) n=4,l=1;(ii) n=4,l=0;(iii) n=3,l=2;(iv) n=3,l=1 can be placed into order of increasing energy,from the lowest to highest,as :

$\begin{array}{1 1}(a)\;(iv) < (ii) < (iii) < (i)\\(b)\;(ii) < (iv) < (i) < (iii)\\(c)\;(i) < (iii) < (ii) < (iv)\\(d)\;(iii) < (i) < (iv) < (ii)\end{array}$

Higher is the value of $(n+l)$,more is the energy level of orbital.If $(n+l)$ is same,lower value of n decides lower energy level.
Hence (a) is the correct answer.