1. As fall arrived and school began, D'Aloisio felt immense pressure to deliver for his backers. He needed to whip his algorithm into better shape, so he contracted a team of Israeli coders who specialize in natural language processing. Searching on Google, he found and hired a retired professor living in Thailand who'd written seminal books on the topic. 'He became our main scientist,' says D'Aloisio. 'He now works at Yahoo! in the Sunnyvale office.'
2. The number of such applications in Beijing last year increased 426% from that of 2015.
3. The sharp decline in unemployment will start to seem real
4. v. 加强，变坚固
5. adj. 被识别的；经鉴定的；被认同者 v. 鉴定（id
6. The spread of HIV through drug injections has been effectively controlled. In 2017, the number of people infected through drug abuse was 44.5 percent lower than that in 2012.