Câu hỏi:

DO ALL VOLCANOES ERUPT?

Some volcanoes are always erupting. They are called active volcanoes. Mount Etna in Italy is an active volcano. Some volcanoes have not ______(4) ______ since prehistoric times. These are called extinct volcanoes. Most of the Hawaiian Islands are extinct volcanoes. These volcanoes ___(5) ______ have a hot spot under them. They cannot erupt anymore. Some volcanoes have not erupted for a long time, so they could erupt again. These are called dormant volcanoes. Scientists try to figure out when volcanoes will erupt. Studying volcanoes is hard and dangerous work. Scientists drill into volcanoes. They create maps of the inside of the volcanoes. They use satellites to study volcanoes in space. Scientists have been able to predict a few eruptions, _____(6) ______it is not easy to tell what a volcano might do. (4)

Some volcanoes have not ______(4) ______ since prehistoric times.