$Y=\frac{2+4+6+8+..+2n}{n}$
$X=\frac{3+5+7+..+(2n+1)}{n}$
$X=\frac{(2+1)+(4+1)+(6+1)+..+(2n+1)}{n}$
$X=\frac{2+4+6+8..+2n}{n}+\frac{1+1+1+1+..+n\ times}{n}$
$X=\frac{2+4+6+8..+2n}{n}+\frac{n}{n}$
$X=Y+1$
X-Y = Y+1-Y = 1
Hence,Option(2)1 is the correct choice.