Three elements $X,Y$ and $Z$ are in the $3^{rd}$ period of the periodic table. The oxides of $X,Y$ and $Z$, respectively, are basic, amphoteric and acidic. The correct order of the atomic numbers of $X,Y$ and $Z$ is :

The correct option is A $X<Y<Z$
On moving left to right in a period, acidic character of oxides increases.
$3^{rd}$ period element oxides:

On moving from left to right in $3^{rd}$ period,
Acidic character $\uparrow$
Atomic number $\uparrow$
So, $Z$ have maximum atomic number
& $X$ have minimum atomic Number.
So, correct order is $X<Y<Z$
Correct option is (a).