Input: Article: DC systems (especially third-rail systems) are limited to relatively low voltages and this can limit the size and speed of trains and cannot use low-level platform and also limit the amount of air-conditioning that the trains can provide. This may be a factor favouring overhead wires and high-voltage AC, even for urban usage. In practice, the top speed of trains on third-rail systems is limited to 100 mph (160 km/h) because above that speed reliable contact between the shoe and the rail cannot be maintained.

Now answer this question: What can become unreliable if the speed exceeds the limit of 100 mph for DC system trains?

Output: contact between the shoe and the rail

Input: Article: Child labour is still common in many parts of the world. Estimates for child labour vary. It ranges between 250 and 304 million, if children aged 5–17 involved in any economic activity are counted. If light occasional work is excluded, ILO estimates there were 153 million child labourers aged 5–14 worldwide in 2008. This is about 20 million less than ILO estimate for child labourers in 2004. Some 60 percent of the child labour was involved in agricultural activities such as farming, dairy, fisheries and forestry. Another 25 percent of child labourers were in service activities such as retail, hawking goods, restaurants, load and transfer of goods, storage, picking and recycling trash, polishing shoes, domestic help, and other services. The remaining 15 percent laboured in assembly and manufacturing in informal economy, home-based enterprises, factories, mines, packaging salt, operating machinery, and such operations. Two out of three child workers work alongside their parents, in unpaid family work situations. Some children work as guides for tourists, sometimes combined with bringing in business for shops and restaurants. Child labour predominantly occurs in the rural areas (70%) and informal urban sector (26%).

Now answer this question: Does child labour exist in the 21st century?

Output: Child labour is still common

Input: Article: A more elaborate form of urban AC is the rhythmic oldies format, which focuses primarily on "old school" R&B and soul hits from the 1960s to the 1990s, including Motown and disco hits. The format includes soul or disco artists such as ABBA, The Village People, The Jackson 5, Donna Summer, Tina Charles, Gloria Gaynor and the Bee Gees. Rhythmic oldies stations still exist today, but target African-Americans as opposed to a mass audience.

Now answer this question: What is the most recent decade music from which music can be heard on a rhythmic oldies station?

Output:
1990s