Why do states set residence requirements

Which is the best example of a primary source ducument useful in the study of history ?

Background information: this is an article by will irvin, a correspondent for the new york tribune. irvin wrote this piece in april 1915, while reporting from the western front. at the time that irvin wrote this piece, the united states had declared neutrality in the war. boulogne, april 25. – the gaseous vapor which the germans used against the french divisions near ypres last thursday, contrary to the rules of the hague convention, introduces a new element into warfare. the attack of last thursday evening was preceded by the rising of a cloud of vapor, greenish gray and iridescent. that vapor settled to the ground like a swamp mist and drifted toward the french trenches on a brisk wind. its effect on the french was a violent nausea and faintness, followed by an utter collapse. it is believed that the germans, who charged in behind the vapor, met no resistance at all, the french at their front being virtually paralyzed. the effect of the noxious trench gas seems to be slow in wearing away. the men come out of their nausea in a state of utter collapse. some of the rescued have already died from the after effects. how many of the men left unconscious in the trenches when the french broke died from the fumes it is impossible to say, since those trenches were at once occupied by the germans. –will irvin, 1915 what were the effects of the poison gas, according to the reporter? a.) the french were victorious over the germans. b.) soldiers suffered from nausea and began to pass out, while some even died. c.) there were few effects, and the battle continued. d.) the gas was yellow and caused the men’s skin to blister.

Where did people have to work with great organization to be successful at farming? a. on the yellow river basin c. on the hangzhou bay b. on the yangzi river basin d. on the hubei basin