单项选择题
（）how to operate a switchboard， I have to ask the office supervisor to show me the correct procedures.
A.Not known B.Not to know C.Not knowing D.Having not known
单项选择题 Thegovernmenthaspromisedtodo（）liesinitspowertoeasethehardshipsofthehomeless.
单项选择题 I’dratheryou（）makeanycommentontheissueforthetimebeing.
单项选择题 Thisyearwe’llproduce（）steelaswedidlastyear.
