He has been absent ________ class for quite a long time.
Either you or I __ to blame for this.
--Was the driving pleasant when you vocationed in Mexico last summer?----No, it ___ for four days when we arrived, so that the roads were very muddy.
Most of us think that the ocean bottom is ___ smooth land.
--Our guests are coming from Shanghai at 10:30.---Oh, I ___ it ___11:30.
--Peter! Hurry up! You ___ on the phone. ---Oh, I ___ .Thank you.