Why have archaeologists been unable to find many ancient chinese edifices?

How do north and central america differ

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)

Which of the following can scientists estimate geologic time? a. observing rock sequences b. radiometric dating c. comparing fossils d. all of these