某工程单代号搭接网络计划如下图所示，其中关键工作是（）。 A.工作A和工作D B.工

                                                               Guitar Player Wanted
       Are you a lover of music? Can you play the guitar? Can you sing or dance? Welcome to our Sunshine
  Rock Band. Please call Mike at 5487-6598 or send an e-mail to sunshine@yahoo. com.  
                                                                Hot Club
       Do you like to play table tennis? Do you want to play it well? Mr Zhang is a good teacher. You  can
  come here every Saturday afternoon from 2:30 to 5:30 Telephone:8665-7868  Address:Room105,
  Lantian Hotel.
                                                                Swimmer Wanted
       Can you swim? Do you like children? Can you teach them to swim on Sundays? Come and join  us.
  Call Joe at 8472-9999 for more information. 
                                                                Summer Job
       Do you like to talk with people? Do you like to write stories? Would you like to work for a magazine?
  Then come and work as a reporter. Please call Karen at 5561-8823.