The correct option is B x+y2 is a rational number between x and y.
Consider, rational numbers 0 and 2, 0−22=−22=−1, which does not lie between 0 and 2.
Consider, rational numbers -3 and -2, −3×−22=62=3, which does not lie between -3 and -2.
Consider, rational numbers 1 and 2 , 1÷22=0.52=0.25, which does not lie between 1 and 2 .
For any rational numbers x and y , x+y2 is a rational number and it always lies between x and y.