He transplanted the rare flowers to the botany garden_______it was the best time for them.

The man put out the cigarette when _______ that smoking was not allowed on the train.

He went to the station hurriedly only ______that the bus had gone away.  

__ was once regarded as impossible has come true.

The boy, one of the so-called rich second generation, forced his parents to buy a new car _____ it might cost.