Question

Column II give period to which element in column I, match them correctly.

Answer 1

Above elements are arranged according to their outer most shell.
Hydrogen - $1s^1$
Sodium - $1s^{2}2s^{2}2p^{6}3s^1$
Calcium - $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^2$
Barium - $\left[Xe\right]6s^2$.
In sodium, the outer most shell is 3 whereas hydrogen has 1 whereas calcium is 4 and finally barium is 6. Hence we will match $A$ to 4, $B$ to 1, $C$ to 2 and $D$ to 3.