Step 1: Arrange the observations in ascending order.
\[
32,\;
36,\;
37,\;
39,\;
40,\;
41,\;
42,\;
43,\;
44,\;
45,\;
46,\;
47,\;
48,\;
50
\]
There are
\[
n=14
\]
observations.
Step 2: Locate the middle observations.
Since \(n\) is even, the median is the average of the
\[
\frac{n}{2}=7^{\text{th}}
\]
and
\[
\left(\frac{n}{2}+1\right)=8^{\text{th}}
\]
observations.
These are
\[
42 \quad \text{and} \quad 43.
\]
Step 3: Calculate the median.
\[
\text{Median}
=
\frac{42+43}{2}
=
42.5.
\]
Step 4: Final conclusion.
\[
\boxed{42.5\text{ kg}}
\]
Hence, the correct option is \(\boxed{(B)}\).