The success of Sumerian irrigation led directly to what major source of conflict between cities?

Disputes over religious beliefs

Competition for control of water

Arguments about establishing trade routes

Disagreements on proper farming techniques

In addition to building strong walls from mud bricks, what other defensive feature did Sumerians often create around their cities?

Tall watchtowers made from scarce wood and stone

A system of underground tunnels for citizens to escape

Large ditches filled with water, which were known as moats

A series of smaller forts built in the nearby hills for defense

To provide shade from the hot sun

To protect against rival communities

To prevent the river from flooding the city

To mark boundaries for religious festivals

The plains lacked natural barriers

They were required by religious law

They helped to control seasonal floods

There was an abundance of mud for bricks