Option 1 -> The passage mentions geoengineering like the underwater curtain but dismisses such measures as "distractions from the real issue."
Option 2 -> Communities weaning off dependency doesn't help glacier survival; it only addresses human adaptation, not the cause of melting.
Option 3 -> The underwater curtain proposal is specifically criticized by experts as a distraction rather than a real solution to glacier loss.
Option 4 -> The passage explicitly states "about 80% of global glaciers...could survive if countries rapidly reduce greenhouse gas emissions."
Hence, Option 4 -> The passage clearly identifies rapid reduction of greenhouse gas emissions through collective global action as the key to saving approximately 80% of the world's glaciers, contrasting this real solution with distracting geoengineering proposals -> correct