Which of the following antenna system conditions will cause a modern solid-state HF transceiver to automatically reduce power?

Modern solid-state transceivers are built with internal protection circuits to prevent damage to their final amplifier transistors. These transistors are highly sensitive to excessive heat and voltage spikes caused by reflected power from a mismatched load. If there is a severe impedance mismatch (resulting in a high SWR), a large amount of RF energy is reflected back into the transceiver. To protect itself from failure, the transceiver detects this high SWR and automatically reduces its RF output power, a feature often called 'foldback'. The other options, such as wind movement or lightning protector grounds, do not directly trigger the radio's automatic power reduction circuitry unless they cause a sudden, severe change in the SWR.