单项选择题
（）formal occasions， you should talk about some world issues or social problems， not about yourself or your family.
A.In B.At C.On D.By
单项选择题 Onlyafterthestudentshavemasteredtherulesofpronunciation（）.
单项选择题 Whynot（）toProfessorSmithforadvice？Heisanexpertinthisfield.
单项选择题 Wehadapartylastmonth，anditwasalotoffun，solet’shave（）onethismonth.
