Problem: Railway electrification system:

DC commutating electric motors, if fitted with laminated pole pieces, become universal motors because they can also operate on AC; reversing the current in both stator and rotor does not reverse the motor. But the now-standard AC distribution frequencies of 50 and 60 Hz caused difficulties with inductive reactance and eddy current losses. Many railways chose low AC frequencies to overcome these problems. They must be converted from utility power by motor-generators or static inverters at the feeding substations or generated at dedicated traction powerstations.

The now-standard DC frequencies are what?
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A: unanswerable

Problem: The convention in the English language is to call nearly all national heads of government "prime minister" (sometimes modified to the equivalent term of premier), regardless of the correct title of the head of government as applied in his or her respective country. The few exceptions to the rule are Germany and Austria, whose heads of government titles are almost always translated as Chancellor; Monaco, whose head of government is referred to as the Minister of State; and Vatican City, for which the head of government is titled the Secretary of State. In the case of Ireland, the head of government is occasionally referred to as the Taoiseach by English speakers. A stand-out case is the President of Iran, who is not actually a head of state, but the head of the government of Iran. He is referred to as "president" in both the Persian and English languages.
What is the term for the highest position in government in Vatican City?
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Answer: Secretary of State

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
Aspiration varies with place of articulation. The Spanish voiceless stops /p t k/ have voice-onset times (VOTs) of about 5, 10, and 30 milliseconds, whereas English aspirated /p t k/ have VOTs of about 60, 70, and 80 ms. Voice-onset time in Korean has been measured at 20, 25, and 50 ms for /p t k/ and 90, 95, and 125 for /p t k/.
Voice-onset times in Armenian measure at 20, 25, and what?
A: unanswerable

Context and question: General Electric heavily contaminated the Hudson River with polychlorinated biphenyls (PCBs) between 1947-77. This pollution caused a range of harmful effects to wildlife and people who eat fish from the river or drink the water. In response to this contamination, activists protested in various ways. Musician Pete Seeger founded the Hudson River Sloop Clearwater and the Clearwater Festival to draw attention to the problem. The activism led to the site being designated by the EPA as one of the superfund sites requiring extensive cleanup. Other sources of pollution, including mercury contamination and sewage dumping, have also contributed to problems in the Hudson River watershed.
What designation did the EPA give to the site of GE's Hudson River pollution
Answer: superfund

Question: Under the millet system, non-Muslim people were considered subjects of the Empire, but were not subject to the Muslim faith or Muslim law. The Orthodox millet, for instance, was still officially legally subject to Justinian's Code, which had been in effect in the Byzantine Empire for 900 years. Also, as the largest group of non-Muslim subjects (or zimmi) of the Islamic Ottoman state, the Orthodox millet was granted a number of special privileges in the fields of politics and commerce, and had to pay higher taxes than Muslim subjects.
Is there an answer to this question: What code had been active for 900 years in the Byzantine empire?

Answer: Justinian's Code

In Europe during the Medieval period, guilds were formed by craftsmen to organise their trades and written contracts have survived, particularly in relation to ecclesiastical buildings. The role of architect was usually one with that of master mason, or Magister lathomorum as they are sometimes described in contemporary documents.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What was the main thing the contracts were had to do with?
Ah, so..
ecclesiastical buildings