You and I could hardly work together, ______?

  Only at that time ______ that he had made a lot of mistakes in his homework.

So hard ______ that we had to wait another day.

Only when he got on the train _________ that he had left his mobile phone at home．

(2013·江苏，27)“Never for a second，”the boy says，“________that my father would come to my rescue.”