Wuhan is the seventh-largest city in China, with a __18__ of more than 11 million people. It has been a major __19__ hub of the country throughout the ages, long known as the "Nine Provinces' Thoroughfare"(九省通衢), and the Wuhan Railway Hub is one of the four most important railway hubs in China. Coincided with the Chinese New Year, which marks a major festival season and the busiest travel period in China, the virus spread quickly to other Chinese provinces.
      The virus has shown evidence of human-to-human transmission. Its incubation period (time from
exposure to onset of symptoms) __20__ from 2 to 14 days, but there is evidence that it may be __21__
during this period and possibly also for several days after recovery. A larger number of people may have
been infected, but not __22__ (especially mild cases). Cases started to be detected in countries other than China, carried by international travellers, typically to major trade partners. Many Chinese New Year Festival events and tourist __23__ have been closed to prevent mass gatherings, including the Forbidden City in Beijing and traditional temple fairs. Hong Kong raised its infectious disease response level to the highest and declared an __24__, cancelling its New Year __25__, closing schools until March and even Hong Kong Disneyland.
【題組】18.
(A) citizen
(B) neighborhood
(C) population
(D) metropolis