4. The correct answer here would be the first option that is the petrochemical industry.
The greatest petrochemical industry up to that point in the world was born in order to supply the ever growing needs for fuel of the American military. This industry spawned from Beaumont-Port Arthur to Corpus Christi that is along the Gulf Coast.
5.The correct answer here is the second option that is the POW provided a cheap source of labor during the World War II.
The country was in war and the threat of food shortage loomed over the United States. The government wanted farmers to produce ever more food but many farmers left this industry in order to join the military or work in some military related industry. Thus POW made a fine choice for workers on the farms.
6.The correct answer here is the third option that is that North Texas produced more crops than ever before.
The land, due to increased demand that was brought upon by the war, cultivated the land to its fullest potential making Texas and therefore the United States of America, the granary for the all of the Allied forces. That is why more crops were being produced then ever before.