Which of the following signal paths is most likely to experience high levels of absorption when the A-index or K-index is elevated?

Explication

An elevated A or K index means charged particles are being dumped into the polar upper atmosphere, so paths that cross the auroral oval pick up heavy absorption and are the first to fail. Transequatorial, sporadic-E, and near-vertical incidence paths lie away from the auroral zone and are far less affected.