We may learn ___ English well by ___ it.

______ by a greater demand for vegetables,farmers have built more green houses.

 I regret _______ you all present that only one job will be offered in the department.

Up till now, full use of this theory has been ________ in building large ocean-going ships.

Shanghai authorities have guaranteed the quality of the city’s drinking water _____ more than 7500 rotting pigs ______ floating on the Huangpu River in the past week.