Problem: Extract the answer to the question from the following context. Question: Which major isotope of uranium is the only one to have a natural abundance lower than 0.1 percent? Context: Natural uranium consists of three major isotopes: uranium-238 (99.28% natural abundance), uranium-235 (0.71%), and uranium-234 (0.0054%). All three are radioactive, emitting alpha particles, with the exception that all three of these isotopes have small probabilities of undergoing spontaneous fission, rather than alpha emission. There are also five other trace isotopes: uranium-239, which is formed when 238U undergoes spontaneous fission, releasing neutrons that are captured by another 238U atom; uranium-237, which is formed when 238U captures a neutron but emits two more, which then decays to neptunium-237; uranium-233, which is formed in the decay chain of that neptunium-237; and finally, uranium-236 and -240, which appear in the decay chain of primordial plutonium-244. It is also expected that thorium-232 should be able to undergo double beta decay, which would produce uranium-232, but this has not yet been observed experimentally.

A: uranium-234

Problem: Extract the answer to the question from the following context. Question: what is the second natural fuel listed Context: Underpinning Houston's land surface are unconsolidated clays, clay shales, and poorly cemented sands up to several miles deep. The region's geology developed from river deposits formed from the erosion of the Rocky Mountains. These sediments consist of a series of sands and clays deposited on decaying organic marine matter, that over time, transformed into oil and natural gas. Beneath the layers of sediment is a water-deposited layer of halite, a rock salt. The porous layers were compressed over time and forced upward. As it pushed upward, the salt dragged surrounding sediments into salt dome formations, often trapping oil and gas that seeped from the surrounding porous sands. The thick, rich, sometimes black, surface soil is suitable for rice farming in suburban outskirts where the city continues to grow.

A: gas

Problem: Extract the answer to the question from the following context. Question: Nanjing was not in the? Context: During the period of NorthSouth division, Nanjing remained the capital of the Southern dynasties for more than two and a half centuries. During this time, Nanjing was the international hub of East Asia. Based on historical documents, the city had 280,000 registered households. Assuming an average Nanjing household had about 5.1 people at that time, the city had more than 1.4 million residents.

A: North

Problem: Extract the answer to the question from the following context. Question: Which took place earlier, the onset of the Crusades or the expulsion of the Jews from France? Context: With the onset of the Crusades in 1095, and the expulsions from England (1290), France (1394), and parts of Germany (15th century), Jewish migration pushed eastward into Poland (10th century), Lithuania (10th century), and Russia (12th century). Over this period of several hundred years, some have suggested, Jewish economic activity was focused on trade, business management, and financial services, due to several presumed factors: Christian European prohibitions restricting certain activities by Jews, preventing certain financial activities (such as "usurious" loans) between Christians, high rates of literacy, near universal male education, and ability of merchants to rely upon and trust family members living in different regions and countries.

A:
onset of the Crusades