What is a reason Sumer declines as a civilization?

A- Sumerian rulers fought to gain territory

B- the Tigris and Euphrates rivers dried up

C- the climate changes drastically

D- Sumerian rulers outlawed religion

My guess is A

6 answers

You are correct.
http://en.wikipedia.org/wiki/Sumer#Decline

The actual reason is that population went north, more dependence on irrigated fields, so the soil got more and more salty, and production decreased. You have to flush soils in irrigated lands, especially in hot arid regions (like Texas and Sumeria). No answer above is good, the instructor might be thinking either B or C, but in fact, neither is correct, it was just too much pressure on an arid land without enough flushing water. The rives were not drying up, all the water was being used by irrigation,at least the Tigris. So maybe that is what your instructor means on B.
And then again, maybe MsSue is right, but I suspect salty land played an important part.
It may be that the rulers sought more territory because their own was becoming unsuitable for agriculture.
Ok, Thank you both very much! I strongly appreciate it :)
You're very welcome.