Problem: Copyright infringement:

In some countries, the personal copying exemption explicitly requires that the content being copied was obtained legitimately – i.e., from authorized sources, not file-sharing networks. Other countries, such as the Netherlands, make no such distinction; the exemption there had been assumed, even by the government, to apply to any such copying, even from file-sharing networks. However, in April 2014, the Court of Justice of the European Union ruled that "national legislation which makes no distinction between private copies made from lawful sources and those made from counterfeited or pirated sources cannot be tolerated." Thus, in the Netherlands, for example, downloading from file-sharing networks is no longer legal.

What does the personal copying exemption explicitly need?
---
A: was obtained legitimately


Problem: Railway electrification system:

Energy sources unsuitable for mobile power plants, such as nuclear power, renewable hydroelectricity, or wind power can be used. According to widely accepted global energy reserve statistics, the reserves of liquid fuel are much less than gas and coal (at 42, 167 and 416 years respectively). Most countries with large rail networks do not have significant oil reserves and those that did, like the United States and Britain, have exhausted much of their reserves and have suffered declining oil output for decades. Therefore, there is also a strong economic incentive to substitute other fuels for oil. Rail electrification is often considered an important route towards consumption pattern reform. However, there are no reliable, peer-reviewed studies available to assist in rational public debate on this critical issue, although there are untranslated Soviet studies from the 1980s.

What research can be used in the future if translated?
---
A: Soviet studies from the 1980s


Problem: Mesozoic:

Sea levels began to rise during the Jurassic, which was probably caused by an increase in seafloor spreading. The formation of new crust beneath the surface displaced ocean waters by as much as 200 m (656 ft) more than today, which flooded coastal areas. Furthermore, Pangaea began to rift into smaller divisions, bringing more land area in contact with the ocean by forming the Tethys Sea. Temperatures continued to increase and began to stabilize. Humidity also increased with the proximity of water, and deserts retreated.

Why did humidity decrease during the Jurassic?
---
A: unanswerable


Problem: Han dynasty:

Even before Han's expansion into Central Asia, diplomat Zhang Qian's travels from 139 to 125 BC had established Chinese contacts with many surrounding civilizations. Zhang encountered Dayuan (Fergana), Kangju (Sogdiana), and Daxia (Bactria, formerly the Greco-Bactrian Kingdom); he also gathered information on Shendu (Indus River valley of North India) and Anxi (the Parthian Empire). All of these countries eventually received Han embassies. These connections marked the beginning of the Silk Road trade network that extended to the Roman Empire, bringing Han items like silk to Rome and Roman goods such as glasswares to China.

What empire had established an embassy in Anxi?
---
A:
Han