explain why are so many oil refineries were set up along the southeastern border of Texas.

There are oil fields spread throughout Texas and many of then are set up along the coastline.  The reason is that its economical. Prospectors had to drill oil where they could find it, but they could choose where they placed the refineries. Some refineries were set up near the oil fields. Those in the oil industry quickly determined that it was cheaper to ship their product throughout the U.S. overseas than to send it over land, so they built refineries along the coast. This allowed for easy access to the cargo ships once the oil was turned into its designated product.

b). (sounds as the best answer)

the hyksos invasion. the hyksos were able to attack egypt successfully because of their skills in using bronze weapons, composite bows and the use of the horse and chariot during the invasion. although the egyptians depict a barbarian-type overthrow, the truth is the seizure was likely a relatively peaceful one.