来自林乐新的问题
【Usingcellphonestochatonline_______verycommonamongmiddleschoolstudents.A.beB.isC.areD.am】
Usingcellphonestochatonline_______verycommonamongmiddleschoolstudents.
A.be
B.is
C.are
D.am


【Usingcellphonestochatonline_______verycommonamongmiddleschoolstudents.A.beB.isC.areD.am】
Usingcellphonestochatonline_______verycommonamongmiddleschoolstudents.
A.be
B.is
C.are
D.am
B.is
动名词做主语,谓语动词用单数