________ all the homework assigned by the school,the students have to work at it till midnight.
A.Completing B.To complete
C.Having completed D.To have completed
________ all the homework assigned by the school,the students have to work at it till midnight.
A.Completing B.To complete
C.Having completed D.To have completed
B [考查非谓语动词。此处为目的状语, 因此使用不定式,排除A项和C项,而且不强调完成,因此使用不定式的一般式,故选B项。]