The electromagnetic waves of frequency $2\: MHz\: to\: 30\: MHz$ are:

Question

$\begin {array} {1 1} (a)\; In\: ground \: wave\: propagation & \quad (b)\;In\: sky\: wave\: propagation \\ (c)\;In\: microwave\: propagation & \quad (d)\;In\: satellite\: communication \end {array}$