Assertion $(A)$: Television signals are received through sky-wave propagation.
Reason $(R)$: The ionosphere reflects electromagnetic waves of frequencies in the range $(3-30)$ $MHz$.
Choose the correct option.

• A
  $A$ is true,$R$ is true and $R$ is the correct explanation for $A$.
• B
  $A$ is true,$R$ is true but $R$ is not the correct explanation for $A$.
• C
  $A$ is true but $R$ is false.
• D
  $A$ is false but $R$ is true.