Context: The Houston area is a leading center for building oilfield equipment. Much of its success as a petrochemical complex is due to its busy ship channel, the Port of Houston. In the United States, the port ranks first in international commerce and tenth among the largest ports in the world. Unlike most places, high oil and gasoline prices are beneficial for Houston's economy, as many of its residents are employed in the energy industry. Houston is the beginning or end point of numerous oil, gas, and products pipelines:

Question: Of what is Houston a center?
Answer: oilfield equipment

Question: What has the Houston ship channel served to promote into success?
Answer: petrochemical complex

Question: Where does the Port of Houston rank in international commerce?
Answer: first

Question: Where does Houston rate in the size ranking of world ports?
Answer: tenth

Question: What lines begin or end in Houston?
Answer: pipelines

Question: Of what is Texas a center?
Answer: Unanswerable

Question: What has the Texas ship channel served to promote into success?
Answer: Unanswerable

Question:  Where does the Port of Texas rank in international commerce?
Answer: Unanswerable

Question:  Where does Texas rate in the size ranking of world ports?
Answer: Unanswerable

Question:  What lines begin or end in Texas?
Answer: Unanswerable