Which of the following is the space-weather term for an extreme geomagnetic storm?

NOAA's Space Weather Prediction Center categorizes geomagnetic storms using a G-scale that ranges from G1 (minor) to G5 (extreme). A G5 storm indicates massive disturbances in Earth's magnetic field, which can severely impact radio propagation, power grids, and satellite operations. The other options, such as X5, M9, and B9, refer to the classification of solar flares based on their X-ray emissions, not geomagnetic storms. Remembering that 'G' stands for 'Geomagnetic' easily points to the correct answer.