Explanation: When an HF Single Sideband (SSB) transmission sounds garbled, often described as "Donald Duck" speech, it indicates a slight frequency offset between the transmitting station and your receiver. SSB demodulation is very sensitive to these small frequency differences. The **R.I.T. (Receiver Incremental Tuning)** or **Clarifier** control allows you to adjust your receiver's frequency by a small amount, typically a few kilohertz, *independently* of the main tuning dial. This enables you to fine-tune your receiver to exactly match the transmitting station's frequency, correcting the offset and clarifying the garbled audio into intelligible speech. * **A) Changing the receive frequency to either adjacent channel** would cause you to completely lose the signal, as it's not on a different channel but slightly off-frequency on its current channel. * **B) Advising the other vessel that his transmission is faulty** should only be done if you cannot correct the issue on your end, as your receiver might be off-frequency, or their drift might be correctable locally. * **D) Adjusting the squelch control** would only mute background noise when no signal is present or strong enough; it has no effect on the sound quality of an *already received* signal.