Problem: Electric motor:

Large brushes are desired for a larger brush contact area to maximize motor output, but small brushes are desired for low mass to maximize the speed at which the motor can run without the brushes excessively bouncing and sparking. (Small brushes are also desirable for lower cost.) Stiffer brush springs can also be used to make brushes of a given mass work at a higher speed, but at the cost of greater friction losses (lower efficiency) and accelerated brush and commutator wear. Therefore, DC motor brush design entails a trade-off between output power, speed, and efficiency/wear.

What are small brushes favorable for?
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A: unanswerable


Problem: Windows 8:

On February 29, 2012, Microsoft released Windows 8 Consumer Preview, the beta version of Windows 8, build 8250. Alongside other changes, the build removed the Start button from the taskbar for the first time since its debut on Windows 95; according to Windows manager Chaitanya Sareen, the Start button was removed to reflect their view that on Windows 8, the desktop was an "app" itself, and not the primary interface of the operating system. Windows president Steven Sinofsky said more than 100,000 changes had been made since the developer version went public. The day after its release, Windows 8 Consumer Preview had been downloaded over one million times. Like the Developer Preview, the Consumer Preview expired on January 15, 2013.

When wasn't the Consumer Preview set to expire?
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A: unanswerable


Problem: Infection:

The isolation of enzymes from infected tissue can also provide the basis of a biochemical diagnosis of an infectious disease. For example, humans can make neither RNA replicases nor reverse transcriptase, and the presence of these enzymes are characteristic of specific types of viral infections. The ability of the viral protein hemagglutinin to bind red blood cells together into a detectable matrix may also be characterized as a biochemical test for viral infection, although strictly speaking hemagglutinin is not an enzyme and has no metabolic function.

What enzyme's absence is characteristic of specific types of viral infections?
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A: unanswerable


Problem: Chinese characters:

Although Chinese characters in Vietnam are now limited to ceremonial uses, they were once in widespread use. Until the early 20th century, Literary Chinese was used in Vietnam for all official and scholarly writing. Around the 13th century the Nôm script was developed to record folk literature in the Vietnamese language. The script used Chinese characters to represent both borrowed Sino-Vietnamese vocabulary and native words with similar pronunciation or meaning. In addition thousands of new compound characters were created to write Vietnamese words. This process resulted in a highly complex system that was never mastered by more than 5% of the population. Both Literary Chinese and Nôm were replaced in the early 20th century by Vietnamese written with the Latin-based Vietnamese alphabet.

What was used in schooling?
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A:
Literary Chinese