Answer:
They had a surplus of food, they divided labor and built cities.
After the development of the irrigation systems, they could grow more wheat and that meant more food for the growth of the population.
They divided labor between themselves. Who will harvest crops, who will tend to the irrigation systems, who will tend to fields. They had a lot of other workers such as carpenters or soldiers and that means that they knew how to divide labor between the population.
They started to build cities so they could work together, trade, store food, and the cities grew as more and more people came to live there.
You didn't list choices, but the two possible answers would be:
<h2>Germany resumed unrestricted submarine warfare.</h2><h2>The Zimmermann Telegram revealed a German attempt to gain Mexico as an ally against the United States.</h2><h2 />
Context/detail:
Public outrage in the US against the Germans swept the nation following the sinking of the British ocean liner, Lusitania, which had happened in May, 1915. When a German U-boat (submarine) sank the Lusitania, over 1,000 persons were killed, including more than 100 Americans. The passenger liner was targeted by the Germans because they suspected weapons were being shipped to Britain in the cargo hold of the ship.
Germany managed to stave off American entry into the war at the time by pledging to stop submarine attacks. But two years later, the Germans resumed such attacks. This inflamed public opinion against Germany once again and poised America to go to war.
In addition, British intelligence intercepted and decoded a telegram (known as the "Zimmermann Telegram") that showed Germany was trying to secure Mexico as an ally against the United States. The revelation of this plan inflamed feelings in the United States. The telegram was sent in January, 1917. In March, 1917, German Foreign Secretary Arthur Zimmermann admitted the telegram was, in fact, sent by his office.
In April, 1917, the US declared war on Germany in response to the Germans' submarine warfare and the Zimmermann Telegram.
It began in 1790 and ended in 1840
16+8+9
16+17
33 therefore your answer is 33
