What was the basis for the wealth of Ghana, Mali, and Songhai?

Which statement is an example of direct democracy? a) people elect a senator to the u. s. congress. b) the town council approves funding for a new high school. c) the president issues an executive preventing states from executing prisoners. d) voters approve an amendment allowing elderly people to pay nothing in property tax.

The segments shown below could form a triangle.

What new concept did the the american revolution introduce into the world