Food supplies in the flood-stricken area _______. We must act immediately before there’s none left.
A．have run out B．have been run out C．are running out D．are being run out
He _______ have taken your car by mistake because he didn’t have the keys.
A．mustn’t B．shouldn’t C．couldn’t D．needn’t
It is not always easy for the public to see _______ use a new invention can be of to human life.
A．whose B．which C．that D．what
He dressed up and went to the party as if ________.
A．was invited B．had been invited C．to be invited D．invited
After completing and signing it, please return the form to us in the envelope _______.
A．provided B．providing C．having provided D．provide
The book was written in 1946, _______ the education system has witnessed great changes.
A．since then B．when C．since when D．during which
