For the sets of real numbers given by

$R_1=\{(x,y):x∈R, y∈R\,x^2+y^2≤25\}$

$R_2=\{(x,y):x∈R, y∈R\,9y≥4x^2\}$

$R_1∩R_2$ is

none of these

Here $x^2+y^2≤25$ are the elements of R₁ lying with in and on the circle $x^2+y^2=25$, where as $4x^2≤9y$ are the elements of R₂ lying with in and on the parabola $4x^2=9y$.

Hence relation $R_1∩R_2$ is not a function.

Hence (D) is the correct answer.