“Well done, John! Not a single mistake ________ in your exam paper this time!” said the teacher

My sister will get up early tomorrow morning，because the train to London _________at 6:00 a.m

下列各句中，加线词语使用恰当的一句是(　　)

The research on the new flu virus vaccine ischallenging and demanding. Who do you think can do thejob— ____ my students have a try

_______you I owe a thousand apologies________having doubted your ability.[ ]