Through which mode of propagation, the radio waves can be sent from one place to another

Options

A. Ground wave propagation can be sustained at frequencies 500 KHz to 1500 KHz.
B. Sky wave propagation is useful in the range of 30 to 40 MHz.
C. space wave propagation
D. all of them

Explanation

**Step-by-Step Solution:**

1. **Understanding Radio Wave Propagation**: Radio waves can be transmitted from one location to another using different modes of propagation. The three primary modes are ground wave, sky wave, and space wave propagation.

2. **Ground Wave Propagation**: This mode involves the transmission of radio waves along the surface of the Earth. Ground waves can follow the curvature of the Earth and are effective for short to medium distances, especially at lower frequencies.

3. **Sky Wave Propagation**: In this mode, radio waves are transmitted upwards towards the ionosphere, where they are reflected back to the Earth. This allows for long-distance communication, as the waves can bounce off the ionosphere multiple times, covering vast distances.

4. **Space Wave Propagation**: This mode involves the transmission of radio waves directly through space. Space waves can travel in a straight line and are often used for satellite communication. They can also include line-of-sight communication, where the transmitter and receiver are within the direct line of sight.

5. **Conclusion**: All three modes of propagation (ground wave, sky wave, and space wave) can be used to send radio waves from one place to another. Therefore, the answer to the question is that radio waves can be sent through all modes of propagation.

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