It is not a good idea to interrupt the actor Richard Griffiths in the middle of a play.During the past year he has stopped performances at the National Theatre when mobile phones have gone off,and he threw one member of the audience out of a West End play for failing to switch off his phone. So when a mobile rang out for the third time during his performance as Hector,a teacher,in Alan Bennett's The History Boys at the Broadhurst Theatre in New York,he spoke angrily:"I am not going to compete with these electronic devices". Griffiths'actions led a debate in the UK theatre world over whether phones should be forbidden by law from British theatres,too.Actors are already asking the government to legalise   the use of electronic screening   devices to block mobile phone signals from theatres. Technology companies market"blocking"devices that send out a high-powered signal on the same frequency   as a mobile phone,occupying all the available spectrums  . But these are forbidden in many countries because they might prevent emergency calls from being made. Rosemary Squire,president of the Society of West End Theatre and co-founder of the Ambassador Theatre Group,which operates 12West End theatres,said,"Phones are one of the biggest operational problems theatres face.We should look for equipment that could block phones or make a London-wide theatre rule." Nick Allott,the managing director of Sir Cameron Mackintosh's theatre group,said,"We would all welcome some ways of preventing ringing phones,but doctors and emergency workers need to be  paged in a theatre and we mustn't prevent that." According to the passage,"blocking"devices    .
have the same functions as mobile phones prevent the mobile phones being used properly cause the biggest problem theatres have to face help make emergency calls
Question: It is not a good idea to interrupt the actor Richard Griffiths in the middle of a play.During the past year he has stopped performances at the National Theatre when mobile phones have gone off,and he threw one member of the audience out of a West End play for failing to switch off his phone. So when a mobile rang out for the third time during his performance as Hector,a teacher,in Alan Bennett's The History Boys at the Broadhurst Theatre in New York,he spoke angrily:"I am not going to compete with these electronic devices". Griffiths'actions led a debate in the UK theatre world over whether phones should be forbidden by law from British theatres,too.Actors are already asking the government to legalise   the use of electronic screening   devices to block mobile phone signals from theatres. Technology companies market"blocking"devices that send out a high-powered signal on the same frequency   as a mobile phone,occupying all the available spectrums  . But these are forbidden in many countries because they might prevent emergency calls from being made. Rosemary Squire,president of the Society of West End Theatre and co-founder of the Ambassador Theatre Group,which operates 12West End theatres,said,"Phones are one of the biggest operational problems theatres face.We should look for equipment that could block phones or make a London-wide theatre rule." Nick Allott,the managing director of Sir Cameron Mackintosh's theatre group,said,"We would all welcome some ways of preventing ringing phones,but doctors and emergency workers need to be  paged in a theatre and we mustn't prevent that." According to the passage,"blocking"devices    .
A. have the same functions as mobile phones
B. prevent the mobile phones being used properly
C. cause the biggest problem theatres have to face
D. help make emergency calls
Answer: