The correct choice is (c) 4.38m
The explanation is: The radiation resistance of a monopole is 1/8 times the current element.
\(R_{rad}=10\pi^2 (l/\lambda)^2\)
For a monopole height h= l/2 => l= 2h
\(R_{rad}=10\pi^2(\frac{2h}{\lambda})^2=40\pi^2 (\frac{hf}{c})^2=40\pi^2 (\frac{1×100×10^6}{3×10^{10} })^2=4.38m\Omega\)
