单选题 Nobody knows what triggered the event, which______a million cubic meters of water per second, obliterating the barrier between Britain and France.(2008年北京大学考博试题)
【正确答案】 A
【答案解析】解析：各选项的意思是：release释放，排放；relieve解脱，缓解；restore恢复，修理：retain保持，保留。根据句意可知，答案是A。