Concept:
For normal viewing through a medium of refractive index \(\mu\),
\[
\text{Apparent depth}
=
\frac{\text{Real depth}}{\mu}.
\]
When several transparent layers are stacked, the total apparent depth is the sum of the apparent depths of the individual layers.
Step 1: Find the apparent depth of the oil layer.
Depth of oil layer,
\[
\frac{x}{2}.
\]
Its apparent depth is
\[
d_1
=
\frac{\frac{x}{2}}{\mu_1}
=
\frac{x}{2\mu_1}.
\]
Step 2: Find the apparent depth of the water layer.
Depth of water layer,
\[
\frac{x}{2}.
\]
Its apparent depth is
\[
d_2
=
\frac{\frac{x}{2}}{\mu_2}
=
\frac{x}{2\mu_2}.
\]
Step 3: Calculate the total apparent depth.
\[
d
=
d_1+d_2.
\]
\[
d
=
\frac{x}{2\mu_1}
+
\frac{x}{2\mu_2}.
\]
\[
d
=
\frac{x}{2}
\left(
\frac{1}{\mu_1}
+
\frac{1}{\mu_2}
\right).
\]
\[
d
=
\frac{x}{2}
\left(
\frac{\mu_1+\mu_2}{\mu_1\mu_2}
\right).
\]
\[
d
=
\frac{x(\mu_1+\mu_2)}
{2\mu_1\mu_2}.
\]
Step 4: Write the final answer.
\[
\boxed{
d=
\frac{x(\mu_1+\mu_2)}
{2\mu_1\mu_2}
}
\]
\[
\boxed{\text{Answer = (A)}}
\]