Answer: A
Eruptions are unstoppable, and a very large one is potentially long lasting (several days of intense explosive output from the volcano). Further, the effects are both immediate (widespread ash fall, pyroclastic flows) and also of longer-duration (due atmospheric aerosols, re-sedimentation of fresh deposits by lahar activity), persisting and presenting problems for years afterwards. In these ways, the hazards posed by explosive eruptions differ from those due to all other natural disasters. It will necessary to develop strategies to minimize and cope with the effects of future major eruptions. The economic cost of recovery from any future large-scale eruptions will be a major burden on society. Finally, as airborne ash and atmospheric sulphate aerosols will bring about the most widespread, long-lasting and generally hazardous effects of the next large explosive eruption, it will be essential to carry out further studies with global circulation atmospheric models to evaluate their potential effects on climate and weather, and other potential feedbacks with global environmental cycles. Some currently unanticipated consequences will surely be found.