Input: Hydrogen
The energy levels of hydrogen can be calculated fairly accurately using the Bohr model of the atom, which conceptualizes the electron as "orbiting" the proton in analogy to the Earth's orbit of the Sun. However, the electromagnetic force attracts electrons and protons to one another, while planets and celestial objects are attracted to each other by gravity. Because of the discretization of angular momentum postulated in early quantum mechanics by Bohr, the electron in the Bohr model can only occupy certain allowed distances from the proton, and therefore only certain allowed energies.

What attracts planets and celestial items?
Output: gravity


Input: Article: Early court cases focused on the liability of Internet service providers (ISPs) for hosting, transmitting or publishing user-supplied content that could be actioned under civil or criminal law, such as libel, defamation, or pornography. As different content was considered in different legal systems, and in the absence of common definitions for "ISPs," "bulletin boards" or "online publishers," early law on online intermediaries' liability varied widely from country to country. The first laws on online intermediaries' liability were passed from the mid-1990s onwards.[citation needed]

Now answer this question: When were the first laws of liability passed?

Output: mid-1990s


Article: The return of former player George Graham as manager in 1986 brought a third period of glory. Arsenal won the League Cup in 1987, Graham's first season in charge. This was followed by a League title win in 1988–89, won with a last-minute goal in the final game of the season against fellow title challengers Liverpool. Graham's Arsenal won another title in 1990–91, losing only one match, won the FA Cup and League Cup double in 1993, and a second European trophy, the European Cup Winners' Cup, in 1994. Graham's reputation was tarnished when he was found to have taken kickbacks from agent Rune Hauge for signing certain players, and he was dismissed in 1995. His replacement, Bruce Rioch, lasted for only one season, leaving the club after a dispute with the board of directors.

Question: What competitor did Arsenal defeat to win a league title in the 1988-89 season?
Ans: Liverpool


Here is a question about this article: In 1983, New York State Attorney General Robert Abrams filed suit in the United States District Court for the Northern District of New York to compel GE to pay for the cleanup of what was claimed to be more than 100,000 tons of chemicals dumped from their plant in Waterford, New York. In 1999, the company agreed to pay a $250 million settlement in connection with claims it polluted the Housatonic River (Pittsfield, Massachusetts) and other sites with polychlorinated biphenyls (PCBs) and other hazardous substances.
What is the answer to this question: In which year was a settlement reached regarding GE's pollution of the Housatonic River?
****
So... 1999


The problem: Answer a question about this article:
Improvisation once played an important role in classical music. A remnant of this improvisatory tradition in classical music can be heard in the cadenza, a passage found mostly in concertos and solo works, designed to allow skilled performers to exhibit their virtuoso skills on the instrument. Traditionally this was improvised by the performer; however, it is often written for (or occasionally by) the performer beforehand. Improvisation is also an important aspect in authentic performances of operas of Baroque era and of bel canto (especially operas of Vincenzo Bellini), and is best exemplified by the da capo aria, a form by which famous singers typically perform variations of the thematic matter of the aria in the recapitulation section ('B section' / the 'da capo' part). An example is Beverly Sills' complex, albeit pre-written, variation of Da tempeste il legno infranto from Händel's Giulio Cesare.
What can solo performers exhibit during a cadenza?
****
The answer: their virtuoso skills on the instrument


The problem: Answer a question about this article:
Infrared reflectography (fr; it; es), as called by art conservators, can be applied to paintings to reveal underlying layers in a completely non-destructive manner, in particular the underdrawing or outline drawn by the artist as a guide. This often reveals the artist's use of carbon black, which shows up well in reflectograms, as long as it has not also been used in the ground underlying the whole painting. Art conservators are looking to see whether the visible layers of paint differ from the underdrawing or layers in between – such alterations are called pentimenti when made by the original artist. This is very useful information in deciding whether a painting is the prime version by the original artist or a copy, and whether it has been altered by over-enthusiastic restoration work. In general, the more pentimenti the more likely a painting is to be the prime version. It also gives useful insights into working practices.
What shows up particularly well in reflectograms?
****
The answer:
carbon black