Explanation:

- Radio waves are a form of electromagnetic radiation with frequencies in the range from about 3 kHz to 300 GHz.

- The 30-meter band refers to the wavelength of the radio waves. According to the formula \( \text{Frequency (Hz)} = \frac{300,000,000 \text{ m/s}}{\text{Wavelength (m)}} \).

- For a 30-meter band, the frequency is \( \frac{300,000,000}{30} = 10,000,000 \) Hz or 10 MHz.

- Option 1: 10 MHz

- Correct frequency for a 30-meter band.

- CORRECT ANSWER

- Option 2: 10 kHz

- Too low for a 30-meter band.

- Option 3: \(3 \times 10^{10}\) Hz

- Too high for a 30-meter band.

- Option 4: \(19 \times 10^{11}\) Hz

- Also too high.