instruction:
This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.
question:
Passage: Naturally occurring glass, especially the volcanic glass obsidian, has been used by many Stone Age societies across the globe for the production of sharp cutting tools and, due to its limited source areas, was extensively traded. But in general, archaeological evidence suggests that the first true glass was made in coastal north Syria, Mesopotamia or ancient Egypt. The earliest known glass objects, of the mid third millennium BCE, were beads, perhaps initially created as accidental by-products of metal-working (slags) or during the production of faience, a pre-glass vitreous material made by a process similar to glazing. Question: What was obsidian used to make in prehistoric times?
answer:
cutting tools

question:
Passage: During the Franco-Prussian War and the Siege of Strasbourg, the city was heavily bombarded by the Prussian army. The bombardment of the city was meant to break the morale of the people of Strasbourg. On 24 and 26 August 1870, the Museum of Fine Arts was destroyed by fire, as was the Municipal Library housed in the Gothic former Dominican church, with its unique collection of medieval manuscripts (most famously the Hortus deliciarum), rare Renaissance books, archeological finds and historical artifacts. The gothic cathedral was damaged as well as the medieval church of Temple Neuf, the theatre, the city hall, the court of justice and many houses. At the end of the siege 10,000 inhabitants were left without shelter; over 600 died, including 261 civilians, and 3200 were injured, including 1,100 civilians. Question: Who bombarded the city of Strasbourg?
answer:
Prussian army

question:
Passage: The city shares a 15-mile (24 km) border with Mexico that includes two border crossings. San Diego hosts the busiest international border crossing in the world, in the San Ysidro neighborhood at the San Ysidro Port of Entry. A second, primarily commercial border crossing operates in the Otay Mesa area; it is the largest commercial crossing on the California-Baja California border and handles the third-highest volume of trucks and dollar value of trade among all United States-Mexico land crossings. Question: Where is San Diego's border crossing?
answer:
the San Ysidro neighborhood at the San Ysidro Port of Entry