Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
Many sensor systems rely on light as the signal source. LEDs are often ideal as a light source due to the requirements of the sensors. LEDs are used as motion sensors, for example in optical computer mice. The Nintendo Wii's sensor bar uses infrared LEDs. Pulse oximeters use them for measuring oxygen saturation. Some flatbed scanners use arrays of RGB LEDs rather than the typical cold-cathode fluorescent lamp as the light source. Having independent control of three illuminated colors allows the scanner to calibrate itself for more accurate color balance, and there is no need for warm-up. Further, its sensors only need be monochromatic, since at any one time the page being scanned is only lit by one color of light. Since LEDs can also be used as photodiodes, they can be used for both photo emission and detection. This could be used, for example, in a touchscreen that registers reflected light from a finger or stylus. Many materials and biological systems are sensitive to, or dependent on, light. Grow lights use LEDs to increase photosynthesis in plants, and bacteria and viruses can be removed from water and other substances using UV LEDs for sterilization.
non- What device uses infrared LEDs to measure oxygen saturation?
A: unanswerable

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
By 1790, the Jewish population of Alsace was approximately 22,500, about 3% of the provincial population. They were highly segregated and subject to long-standing anti-Jewish regulations. They maintained their own customs, Yiddish language, and historic traditions within the tightly-knit ghettos; they adhered to Talmudic law enforced by their rabbis. Jews were barred from most cities and instead lived in villages. They concentrated in trade, services, and especially in money lending. They financed about a third of the mortgages in Alsace. Official tolerance grew during the French Revolution, with full emancipation in 1791. However, local antisemitism also increased and Napoleon turned hostile in 1806, imposing a one-year moratorium on all debts owed to Jews.[citation needed] In the 1830-1870 era most Jews moved to the cities, where they integrated and acculturated, as antisemitism sharply declined. By 1831, the state began paying salaries to official rabbis, and in 1846 a special legal oath for Jews was discontinued. Antisemitic local riots occasionally occurred, especially during the Revolution of 1848. Merger of Alsace into Germany in 1871-1918 lessened antisemitic violence.
Which country was Alsace merged into during  1871-1918
A: Germany

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
Evidence of wheeled vehicles appeared in the mid 4th millennium BC, near-simultaneously in Mesopotamia, the Northern Caucasus (Maykop culture) and Central Europe. The wheel initially took the form of the potter's wheel. The new concept quickly led to wheeled vehicles and mill wheels. The Sumerians' cuneiform writing system is the oldest (or second oldest after the Egyptian hieroglyphs) which has been deciphered (the status of even older inscriptions such as the Jiahu symbols and Tartaria tablets is controversial). The Sumerians were among the first astronomers, mapping the stars into sets of constellations, many of which survived in the zodiac and were also recognized by the ancient Greeks. They were also aware of the five planets that are easily visible to the naked eye.
How many planets were the Sumerians aware of?
A: five

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
Apple was initially reluctant to embrace mice with multiple buttons and scroll wheels. Macs did not natively support pointing devices that featured multiple buttons, even from third parties, until Mac OS X arrived in 2001. Apple continued to offer only single button mice, in both wired and Bluetooth wireless versions, until August 2005, when it introduced the Mighty Mouse. While it looked like a traditional one-button mouse, it actually had four buttons and a scroll ball, capable of independent x- and y-axis movement. A Bluetooth version followed in July 2006. In October 2009, Apple introduced the Magic Mouse, which uses multi-touch gesture recognition (similar to that of the iPhone) instead of a physical scroll wheel or ball. It is available only in a wireless configuration, but the wired Mighty Mouse (re-branded as "Apple Mouse") is still available as an alternative. Since 2010, Apple has also offered the Magic Trackpad as a means to control Macintosh desktop computers in a way similar to laptops.
What did Apple introduce to take the place of a physical scroll wheel in 2009?
A:
multi-touch gesture recognition