Please awnser I will brainlist

Who gave the famous "i have a dream" speech at the march on washington?

Before they can be published, scientific papers must be peer-reviewed. this means that: a) some other scientific experts read the papers and guarantee that they are true. b) some other scientific experts read the papers and provide quality control by eliminating many mistakes. c) an editor reads the papers, to make sure that all the semicolons are in the correct places. d) everyone in the world is given the opportunity to comment on the papers through a specially maintainedblog. e) government bureaucrats read the papers, to be sure that the papers do not insult the political positions ofthe current officeholders.

What is one reason people several different parts of north and south america develop different cultures