To simplify the expression \(\frac{36}{\sqrt{400}}\), we first evaluate \(\sqrt{400}\):
\[
\sqrt{400} = 20
\]
Now we substitute this back into the expression:
\[
\frac{36}{\sqrt{400}} = \frac{36}{20}
\]
Next, we simplify the fraction:
\[
\frac{36}{20} = \frac{18}{10} = \frac{9}{5}
\]
Since the question asks for the answer in simplest radical form and to rationalize the denominator if necessary, it seems like the expression was meant to be different. However, if we needed to keep it with radicals, the original calculation remains correct. Thus, since the denominator \( \sqrt{400} = 20\) is already rational, we do not need to rationalize further.
But if the intent was to present the answer in a way consistent with the listed options and reformulate in a beneficial way, the direct expression is as follows:
Since none of the provided responses reflect \(\frac{9}{5}\), we can check what the other options yield in context.
To clarify, based on the original expression provided:
- If you may refer to \(\frac{36 \sqrt{400}}{400}\) that stays somewhat consistent, the evaluation would yield:
\(\frac{36 \sqrt{400}}{400} = \frac{36 \cdot 20}{400} = \frac{720}{400} = \frac{18}{10} = \frac{9}{5}\), also significant to showcase since original was directed towards \(\sqrt{400}\) being direct:
Thus the ideal answer to \( \frac{36}{\sqrt{400}} \) remains:
\[
\frac{9}{5} \text{ directly, ensuring correctness}
\]
Does not distinctly fit the options; myself pointing for clarity on original processing, let's finalize having clarity on these reflection levels, maintain that adjusting roots holds values as equally reflective towards outcomes.