单项选择题
A.at B.in C.on D.to
I'm tired. I（）working very hard.A.haveB.amC.hadD.have b...
单项选择题I'm tired. I（）working very hard.
A.have B.am C.had D.have been
They（）for hours.A.have been drivingB.have been drivenC....
单项选择题They（）for hours.
A.have been driving B.have been driven C.drove D.drive
He has（）four successful books.A.wroteB.writtenC.been wr...
单项选择题He has（）four successful books.
A.wrote B.written C.been writing
