Step 1: Use the relation between \(K_p\) and \(K_c\).
For a gaseous equilibrium,
\[
K_p=K_c(RT)^{\Delta n}
\]
where
\[
\Delta n
=
(\text{moles of gaseous products})
-
(\text{moles of gaseous reactants})
\]
Step 2: Calculate \(\Delta n\) for the given reaction.
Given reaction:
\[
CO(g)+\frac{1}{2}O_2(g)\rightleftharpoons CO_2(g)
\]
Number of moles of gaseous products:
\[
n_p=1
\]
Number of moles of gaseous reactants:
\[
n_r=1+\frac{1}{2}
=
\frac{3}{2}
\]
Therefore,
\[
\Delta n
=
1-\frac{3}{2}
=
-\frac{1}{2}
\]
Step 3: Substitute \(\Delta n\) into the formula.
\[
K_p
=
K_c(RT)^{-1/2}
\]
Therefore,
\[
\frac{K_p}{K_c}
=
(RT)^{-1/2}
\]
Step 4: Simplify the expression.
Using the property
\[
a^{-1/2}
=
\frac{1}{\sqrt{a}}
\]
we get
\[
\frac{K_p}{K_c}
=
\frac{1}{\sqrt{RT}}
\]
Step 5: Final conclusion.
Hence,
\[
\boxed{\frac{K_p}{K_c}=\frac{1}{\sqrt{RT}}}
\]
Therefore, option (4) is correct.