Among the following which one is wrong for sky wave propagation?

The correct answer is option (4) : Sky waves are radio waves of very high frequency 30 MHz to 300 MHz

Sky wave propagation, also known as ionospheric propagation is the mode of propagation in which electromagnetic waves from antenna are reflected back to earth by atmosphere.

The permitted frequency ranges from 3MHz to 30 MHz. Short wave radio services use sky wave propagation.

It is also used for satellite communication.

Hence the fourth option is wrong.