Problem: Geological history of Earth:

During the Miocene continents continued to drift toward their present positions. Of the modern geologic features, only the land bridge between South America and North America was absent, the subduction zone along the Pacific Ocean margin of South America caused the rise of the Andes and the southward extension of the Meso-American peninsula. India continued to collide with Asia. The Tethys Seaway continued to shrink and then disappeared as Africa collided with Eurasia in the Turkish-Arabian region between 19 and 12 Ma (ICS 2004). Subsequent uplift of mountains in the western Mediterranean region and a global fall in sea levels combined to cause a temporary drying up of the Mediterranean Sea resulting in the Messinian salinity crisis near the end of the Miocene.

What seaway opened as Africa collided with Eurasia?
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A: unanswerable

Problem: Light-emitting diode:

In the late 1980s, key breakthroughs in GaN epitaxial growth and p-type doping ushered in the modern era of GaN-based optoelectronic devices. Building upon this foundation, Dr. Moustakas at Boston University patented a method for producing high-brightness blue LEDs using a new two-step process. Two years later, in 1993, high-brightness blue LEDs were demonstrated again by Shuji Nakamura of Nichia Corporation using a gallium nitride growth process similar to Dr. Moustakas's. Both Dr. Moustakas and Mr. Nakamura were issued separate patents, which confused the issue of who was the original inventor (partly because although Dr. Moustakas invented his first, Dr. Nakamura filed first).[citation needed] This new development revolutionized LED lighting, making high-power blue light sources practical, leading to the development of technologies like BlueRay, as well as allowing the bright high resolution screens of modern tablets and phones.[citation needed]

Who first patented a method to produce high-brightness red LEDs?
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A: unanswerable

Problem: Solar energy:

A solar balloon is a black balloon that is filled with ordinary air. As sunlight shines on the balloon, the air inside is heated and expands causing an upward buoyancy force, much like an artificially heated hot air balloon. Some solar balloons are large enough for human flight, but usage is generally limited to the toy market as the surface-area to payload-weight ratio is relatively high.

Why is the use of solar balloons typically limited to the toy market?
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A: the surface-area to payload-weight ratio is relatively high

Problem: Frederic Chopin:

Chopin seldom performed publicly in Paris. In later years he generally gave a single annual concert at the Salle Pleyel, a venue that seated three hundred. He played more frequently at salons, but preferred playing at his own Paris apartment for small groups of friends. The musicologist Arthur Hedley has observed that "As a pianist Chopin was unique in acquiring a reputation of the highest order on the basis of a minimum of public appearancesfew more than thirty in the course of his lifetime." The list of musicians who took part in some of his concerts provides an indication of the richness of Parisian artistic life during this period. Examples include a concert on 23 March 1833, in which Chopin, Liszt and Hiller performed (on pianos) a concerto by J.S. Bach for three keyboards; and, on 3 March 1838, a concert in which Chopin, his pupil Adolphe Gutmann, Charles-Valentin Alkan, and Alkan's teacher Joseph Zimmermann performed Alkan's arrangement, for eight hands, of two movements from Beethoven's 7th symphony. Chopin was also involved in the composition of Liszt's Hexameron; he wrote the sixth (and final) variation on Bellini's theme. Chopin's music soon found success with publishers, and in 1833 he contracted with Maurice Schlesinger, who arranged for it to be published not only in France but, through his family connections, also in Germany and England.

Where did Chopin prefer to play for people?
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A:
apartment