Which one of the following statements is wrong?
A. 1. Ground wave propagation can be sustained at frequencies 500 KHz to 1500 KHz.
B. 2. Satellite communication is useful for the frequencies above 30 MHz.
C. 3. Sky wave propagation is useful in the range of 30 to 40 MHz.
D. 4. Space wave propagation takes place through tropospheric space.