One of the many aspects of "normal" life that SARS-CoV-2 took away was the enjoyment of live musical performances.With the easing of lockdowns and restrictions in many parts of the world，performers can entertain audiences once again，but concerns about spreading the virus remain.Now，a research reported in ACS Environmental Au have studied aerosol （懸浮顆粒） production from playing wind instruments，singing and acting，allowing them to develop recommendations to minimize COVID transmission.
   Early in the pandemic，COVID-19 outbreaks from choir performances indicated that singing carries a potential infection risk，but less is known about the risks of airborne infection from wind instruments.To help keep performers，audiences and music students safe，Tehya Stockman，Shelly Miller and colleagues wanted to examine aerosol production and flow in the air from various musical activities，as well as test different solutions.
   The researchers examined the extent and speed of air circulation，or small drops of substances，coming from singers' and actors' mouths and from wind instruments，such as the flute，clarinet （單簧管），trumpet and saxophone.They also measured airborne aerosols and carbon dioxide levels exhaled from the performers.They found that aerosol concentrations coming from the bell of a clarinet were comparable to singing.Placing a surgical mask over a singer's face or over the clarinet bell sharply reduced the extent and speed of air circulation and decreased aerosol concentrations in front of the masks.The team then used these measurements to model virus transmission in indoor and outdoor environments，finding that the lowest risk of airborne COVID-19 infection occurred at less than 30 minutes of exposure indoors and less than 60 minutes outdoors.These findings could help musical rehearsals and performances continue in a safer manner for musicians and audiences，the researchers say.

（1）What is the purpose of the research？

C

C

A．To remove lockdowns and restrictions.
B．To promote live musical performances.
C．To find ways to reduce spread of the virus.
D．To reduce aerosol production from instruments.
（2）What have the researchers done to keep people safe？

C

C

A．They have increased air flow from various musical activities.
B．They have indicated that singing carries a possible infection risk.
C．They have tried to measure the risk of infection from instruments.
D．They have found out approaches to preventing aerosol production.
（3）What does the underlined word "exhale" mean in Paragraph 3？

A

A

A．Breath out.
B．Give away.
C．Take in.
D．Test out.
（4）Which of the following is a finding of the research？

B

B

A．Less than 30 minutes of exposure indoors avoids virus transmission.
B．Using a surgical mask can reduce the risks of airborne virus infection.
C．The manner of the musicians and audiences affects the risks of infection.
D．Aerosol concentrations from a clarinet is much more obvious than singing.