According to the islamic calendar and what year did muhammad return to makkah? and what year did muhammad die? what years were these in the christian calendar?

He seventeenth amendment to the us constitution calls for the direct election of all us senators. this means that the people of each state get to vote to decide who will be their two us senators. before this, the legislatures of each state chose the two us senators from that state with no direct involvement of the average voter. why would this amendment be considered a reform? how would it benefit the people? even today some people claim that the seventeenth amendment was a bad idea. what arguments could be made for reverting selection of us senators back to the state legislatures?

What role did the catholic church play in the development of the heliocentric theory promoted by copernicus and galileo?

Which of these is not a criticism of the concentric zone model? it does not accurately describe cities after the rise of suburban development. it only applies to cities that grew after the development of the automobile. it assumes that inner-city areas will always be repurposed instead of abandoned. it places too much importance on the traditional central business district.