The traditional approach __________ with complex problems is to break them down into smaller，more easily managed problems.

Helen borrowed my book _______, saying that she would return it soon.

The country’s 　　　is based on trade.

You know I have no      for foreign languages.

—Do I need to give a tip if I eat at a fast food restaurant in the United States?—Yes , it’s a common       to tip waiters in a restaurant.