Concept:
The standard hyperbola:
\[
\frac{x^2}{a^2}-\frac{y^2}{b^2}=1
\]
has eccentricity:
\[
e=\sqrt{1+\frac{b^2}{a^2}}
\]
An ellipse:
\[
\frac{x^2}{A^2}+\frac{y^2}{B^2}=1
\]
has eccentricity:
\[
e=\sqrt{1-\frac{B^2}{A^2}}
\]
Step 1: Find eccentricity of hyperbola.
Given hyperbola:
\[
2x^2-2y^2=1
\]
\[
\frac{x^2}{1/2}-\frac{y^2}{1/2}=1
\]
Thus,
\[
a^2=b^2=\frac12
\]
Hence eccentricity:
\[
e_h=\sqrt{1+\frac{b^2}{a^2}}
=\sqrt{2}
\]
Step 2: Eccentricity of ellipse.
Given that ellipse eccentricity is reciprocal:
\[
e_e=\frac1{\sqrt2}
\]
So,
\[
1-\frac{B^2}{A^2}=\frac12
\]
\[
\frac{B^2}{A^2}=\frac12
\]
\[
A^2=2B^2
\]
Step 3: Check options.
Option (D):
\[
x^2+2y^2=2
\]
\[
\frac{x^2}{2}+\frac{y^2}{1}=1
\]
Thus,
\[
A^2=2,\quad B^2=1
\]
Indeed,
\[
\frac{B^2}{A^2}=\frac12
\]
Hence correct option is:
\[
\boxed{x^2+2y^2=2}
\]