QUES: But although it meets the definition of outer space, the atmospheric density within the first few hundred kilometers above the Karman line is still sufficient to produce significant drag on satellites. Most artificial satellites operate in this region called low Earth orbit and must fire their engines every few days to maintain orbit.[citation needed] The drag here is low enough that it could theoretically be overcome by radiation pressure on solar sails, a proposed propulsion system for interplanetary travel.[citation needed] Planets are too massive for their trajectories to be significantly affected by these forces, although their atmospheres are eroded by the solar winds.

What system could possibly be used for interplanetary travel?
What is the answer?
ANS: solar sails
QUES: Accurate present day child labour information is difficult to obtain because of disagreements between data sources as to what constitutes child labour. In some countries, government policy contributes to this difficulty. For example, the overall extent of child labour in China is unclear due to the government categorizing child labour data as "highly secret". China has enacted regulations to prevent child labour; still, the practice of child labour is reported to be a persistent problem within China, generally in agriculture and low-skill service sectors as well as small workshops and manufacturing enterprises.
In 2014, the U.S. Department of Labor issued a List of Goods Produced by Child Labor or Forced Labor where China was attributed 12 goods the majority of which were produced by both underage children and indentured labourers. The report listed electronics, garments, toys and coal among other goods.

What is the cause of diagreements in child labour numbers for present day?
What is the answer?
ANS: data sources
QUES: With nitrides containing aluminium, most often AlGaN and AlGaInN, even shorter wavelengths are achievable. Ultraviolet LEDs in a range of wavelengths are becoming available on the market. Near-UV emitters at wavelengths around 375395 nm are already cheap and often encountered, for example, as black light lamp replacements for inspection of anti-counterfeiting UV watermarks in some documents and paper currencies. Shorter-wavelength diodes, while substantially more expensive, are commercially available for wavelengths down to 240 nm. As the photosensitivity of microorganisms approximately matches the absorption spectrum of DNA, with a peak at about 260 nm, UV LED emitting at 250270 nm are to be expected in prospective disinfection and sterilization devices. Recent research has shown that commercially available UVA LEDs (365 nm) are already effective disinfection and sterilization devices. UV-C wavelengths were obtained in laboratories using aluminium nitride (210 nm), boron nitride (215 nm) and diamond (235 nm).

What is the range of wavelengths for cheap UV LEDs?
What is the answer?
ANS:
375395 nm