The problem: Answer a question about this article:
3 kV DC is used in Belgium, Italy, Spain, Poland, the northern Czech Republic, Slovakia, Slovenia, South Africa, Chile, and former Soviet Union countries (also using 25 kV 50 Hz AC). It was formerly used by the Milwaukee Road from Harlowton, Montana to Seattle-Tacoma, across the Continental Divide and including extensive branch and loop lines in Montana, and by the Delaware, Lackawanna & Western Railroad (now New Jersey Transit, converted to 25 kV AC) in the United States, and the Kolkata suburban railway (Bardhaman Main Line) in India, before it was converted to 25 kV 50 Hz AC.
What voltage is being used in railway system of South Africa and Chile?
****
The answer: 3 kV DC

The problem: Answer a question about this article:
Enisa Kafadar argues that there is only one Serbo-Croatian language with several varieties. This has made possible to include all four varieties into a new grammar book. Daniel Buncic concludes that it is a pluricentric language, with four standard variants spoken in Serbia, Croatia, Montenegro and Bosnia and Herzegovina. The mutual intelligibility between their speakers "exceeds that between the standard variants of English, French, German, or Spanish". Other linguists have argued that the differences between the variants of Serbo-Croatian are less significant than those between the variants of English, German,, Dutch, and Hindi-Urdu.
In which areas are the four standard Serbo-Croatian variants spoken?
****
The answer: Serbia, Croatia, Montenegro and Bosnia and Herzegovina.

The problem: Answer a question about this article:
In contrast to the general American Jewish community, which is dwindling due to low fertility and high intermarriage and assimilation rates, the Orthodox Jewish community of the United States is growing rapidly. Among Orthodox Jews, the fertility rate stands at about 4.1 children per family, as compared to 1.9 children per family among non-Orthodox Jews, and intermarriage among Orthodox Jews is practically non-existent, standing at about 2%, in contrast to a 71% intermarriage rate among non-Orthodox Jews. In addition, Orthodox Judaism has a growing retention rate; while about half of those raised in Orthodox homes previously abandoned Orthodox Judaism, that number is declining. According to The New York Times, the high growth rate of Orthodox Jews will eventually render them the dominant demographic force in New York Jewry.
What is the fertility rate among orthodox Jewish families?
****
The answer: 4.1 children

The problem: Answer a question about this article:
Some paleontologists suggest that animals appeared much earlier than the Cambrian explosion, possibly as early as 1 billion years ago. Trace fossils such as tracks and burrows found in the Tonian period indicate the presence of triploblastic worms, like metazoans, roughly as large (about 5 mm wide) and complex as earthworms. During the beginning of the Tonian period around 1 billion years ago, there was a decrease in Stromatolite diversity, which may indicate the appearance of grazing animals, since stromatolite diversity increased when grazing animals went extinct at the End Permian and End Ordovician extinction events, and decreased shortly after the grazer populations recovered. However the discovery that tracks very similar to these early trace fossils are produced today by the giant single-celled protist Gromia sphaerica casts doubt on their interpretation as evidence of early animal evolution.
What produces tracks similar to the fossilized tracks discovered by paleontologists?
****
The answer:
Gromia sphaerica