The locus of foot of perpendicular from the focus to a tangent of the curve $16x^{2}+25y^{2}=400$ is

Question

$$\begin{array}{1 1}(1)x^{2}+y^{2}=4&(2)x^{2}+y^{2}=25\\(3)x^{2}+y^{2}=16&(4)x^{2}+y^{2}=9\end{array}$$