Which phrase best defines the term “opportunity cost”? 1 what a country produces when it specializes in a good or service 2 what a country gives up when it chooses to produce a good or service 3 what a country gains when it chooses to produce a good or service 4 what a country invests in a particular good or service

The yellow river is also known as the huang he river? true or false

Impressions of tropical swamp plants were observed on rocks in polar regions. the impressions were dark black imprints, which means the fossils are examples of ( 1 ) the fossils tell us that polar regions ( 2 ) ( 1 ) a. carbonization b. mineralization c. trace fossils ( 2 ) a. had tropical plants that can grow in ice b. might have had a diffierent climate in the past c. will have abundent vegitation

Plzz on what physical process is responsible for the creation of volcanoes, earthquakes and ocean trenches at the plate margins?