What periods were part of the paleozoic era? a. mesozoic b. pennsylvanian c. cretaceous and d. precambrian googling the answer wont . trust me. i've tried it

The point where two air masses meet is called a

Read the article titled "trans-saharan migration routes to north africa and the eu: historical roots and current trends." why do tens of thousands of sub-saharan africans try to cross the mediterranean each year? how are these refugees commonly portrayed? (site 1)

Read the article about the fraser river, one of the most important rivers in canada. what is the most important species of fish in this river? why are the numbers of these fish declining?