Read the following passage and mark the letter A, B, C, or D to indicate the correct word or phrase that best fits each the numbered blanks

The Covid-19 coronavirus outbreak is a new illness and scientists are still (26) _______ how it spreads from person to person, but similar viruses tend to spread via cough and sneeze droplets. When an infected person coughs or sneezes, they release droplets of saliva or mucus. These droplets can fall on people in the vicinity and can be either directly inhaled or picked up on the hands then (27) _______ when someone touches their face, causing infection. For flu, some hospital guidelines define exposure as being within six feet of an infected person (28) _______ sneezes or coughs for 10 minutes or longer. Viruses can also be spread through droplets landing on surfaces such as seats on buses or trains or desks in school. (29) _______, whether this is a main transmission route depends on how long viruses survive on surfaces – this can vary from hours to months. There is anecdotal evidence that the virus can be spread by people before they have symptoms. Some (30) _______ illnesses such as flu can be passed from one person to another before symptoms occur – but the extent to which this is happening with the new coronavirus is not well understood yet.

                                                                               (Adapted from: https://medihome.com.vn)

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